pwm: raspberrypi-poe: Fix endianness in firmware struct

The reg member of struct raspberrypi_pwm_prop is a little endian 32 bit
quantity. Explicitly convert the (native endian) value to little endian
on assignment as is already done in raspberrypi_pwm_set_property().

This fixes the following sparse warning:

drivers/pwm/pwm-raspberrypi-poe.c:69:24: warning: incorrect type in initializer (different base types)
drivers/pwm/pwm-raspberrypi-poe.c:69:24: expected restricted __le32 [usertype] reg
drivers/pwm/pwm-raspberrypi-poe.c:69:24: got unsigned int [usertype] reg

Fixes: 79caa362eab6 ("pwm: Add Raspberry Pi Firmware based PWM bus")
Signed-off-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/pwm/pwm-raspberrypi-poe.c

···
 					u32 reg, u32 *val)
 {
 	struct raspberrypi_pwm_prop msg = {
-		.reg = reg
+		.reg = cpu_to_le32(reg),
 	};
 	int ret;