pwmcmds: Add Kconfig option to allow boards to disable hardware PWM commands

Some boards may not support hardware based PWM.  Update the build so
that those commands do not need to be compiled if they are not
available.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/Kconfig

@@ -21,6 +21,9 @@ config HAVE_GPIO_ADC
 config HAVE_GPIO_SPI
     bool
     default n
+config HAVE_GPIO_HARD_PWM
+    bool
+    default n
 
 config INLINE_STEPPER_HACK
     # Enables gcc to inline stepper_event() into the main timer irq handler