STM32F4: All pins can do PWM

Marlin/src/HAL/HAL_STM32F4/fastio_STM32F4.h

@@ -31,6 +31,8 @@
 
 #define _BV(b) (1 << (b))
 
+#define USEABLE_HARDWARE_PWM(p) true
+
 #define READ(IO)                digitalRead(IO)
 #define WRITE(IO,V)             digitalWrite(IO,V)
 #define WRITE_VAR(IO,V)         WRITE(IO,V)