pwm: raspberrypi-poe: Fix spelling mistake "Firwmware" -> "Firmware"

There is a spelling mistake in the PWM_RASPBERRYPI_POE Kconfig,
fix it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20250724104148.139559-1-colin.i.king@gmail.com


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>