boards: hw75_keyboard: Restore 72MHz RCC freq

Author: xingrz

config/boards/helloword/hw75_keyboard/hw75_keyboard.dts

@@ -64,14 +64,14 @@
 };
 
 &pll {
-	mul = <6>;
+	mul = <9>;
 	clocks = <&clk_hse>;
 	status = "okay";
 };
 
 &rcc {
 	clocks = <&pll>;
-	clock-frequency = <DT_FREQ_M(48)>;
+	clock-frequency = <DT_FREQ_M(72)>;
 	ahb-prescaler = <1>;
 	apb1-prescaler = <2>;
 	apb2-prescaler = <1>;