Remove virtual from resolve_actual_clock_speed to fix CodeQL alerts (#90)

Calling a virtual method during construction bypasses virtual dispatch.
Since resolve_actual_clock_speed is never called polymorphically through
the base class, remove the virtual declaration from PlatformDma and the
override specifiers from the three platform implementations.

Fixes clang-analyzer-optin.cplusplus.VirtualCall alerts on gdma_dma.cpp,
i2s_dma.cpp, and parlio_dma.cpp.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: stuartparmenter

components/hub75/src/platforms/gdma/gdma_dma.h

@@ -69,7 +69,7 @@ class GdmaDma : public PlatformDma {
   /**
    * @brief Resolve clock speed to achievable frequency (160 MHz / N)
    */
-  HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const override;
+  HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const;
 
   // ============================================================================
   // Pixel API (Direct DMA Buffer Writes)

components/hub75/src/platforms/i2s/i2s_dma.h

@@ -71,7 +71,7 @@ class I2sDma : public PlatformDma {
    * ESP32: max 10 MHz (80 MHz / 2 / 4)
    * ESP32-S2: max 20 MHz (160 MHz / 2 / 4)
    */
-  HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const override;
+  HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const;
 
   // ============================================================================
   // Pixel API (Direct DMA Buffer Writes)

components/hub75/src/platforms/parlio/parlio_dma.h

@@ -46,7 +46,7 @@ class ParlioDma : public PlatformDma {
   /**
    * @brief Resolve clock speed to achievable frequency (160 MHz / N)
    */
-  HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const override;
+  HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const;
 
   void draw_pixels(uint16_t x, uint16_t y, uint16_t w, uint16_t h, const uint8_t *buffer, Hub75PixelFormat format,
                    Hub75ColorOrder color_order, bool big_endian) override;

components/hub75/src/platforms/platform_dma.h

@@ -42,17 +42,6 @@ class PlatformDma {
   const Hub75Config &config_;
   uint16_t lut_[256];  // LUT storage (512 bytes, initialized at runtime)
 
-  /**
-   * @brief Resolve requested clock speed to achievable frequency
-   *
-   * Called from constructor to determine actual clock frequency for BCM timing.
-   * Each platform implements based on its hardware clock divider constraints.
-   *
-   * @param clock_speed Requested clock speed
-   * @return Achievable frequency in Hz
-   */
-  virtual HUB75_CONST uint32_t resolve_actual_clock_speed(Hub75ClockSpeed clock_speed) const = 0;
-
   // ============================================================================
   // Brightness Remapping (Quadratic Curve)
   // ============================================================================