zephyr/boards/frdm_k64f: Improve board configuration.

Changes:
- Enable CONFIG_PWM so that `machine.PWM()` works.
- Increase MicroPython GC heap size.

Signed-off-by: Damien George <[email protected]>

Author: dpgeorge

ports/zephyr/boards/frdm_k64f.conf

@@ -3,6 +3,7 @@ CONFIG_NET_L2_ETHERNET=y
 
 # Hardware features
 CONFIG_I2C=y
+CONFIG_PWM=y
 CONFIG_SPI=y
 
 # Sensor drivers
@@ -14,3 +15,6 @@ CONFIG_FXOS8700_TEMP=y
 CONFIG_FLASH=y
 CONFIG_FLASH_MAP=y
 CONFIG_MPU_ALLOW_FLASH_WRITE=y
+
+# MicroPython config
+CONFIG_MICROPY_HEAP_SIZE=114688