Revert "boards: nxp: pinmux: enable ftm pwm outputs based on DT_INST_* defines"

The DT_INST_* defines for the PWM controllers enabled in the device
tree are always defined causing the LED pins to always be set as PWM
outputs in the pinmux. Revert to using CONFIG_PWM_* for pinmux
configuration for now.

This reverts commit eb42a24d.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>