fix BOARD_NR_PWM_PIN for generic F103C variant

Author: stevstrong

STM32F1/variants/generic_stm32f103c/board/board.h

@@ -64,7 +64,7 @@
 #define BOARD_SPI2_SCK_PIN        PB13
 
 #define BOARD_NR_GPIO_PINS        35
-#define BOARD_NR_PWM_PINS         12
+#define BOARD_NR_PWM_PINS         16
 #define BOARD_NR_ADC_PINS          9
 #define BOARD_NR_USED_PINS         4