leds: pm8058: Silence pointer to integer size warning

The pointer returned by of_device_get_match_data() doesn't have the same
size as u32 on 64-bit architectures, causing a compile warning when
compile-testing the driver on such platform.

Cast the return value of of_device_get_match_data() to unsigned long and
then to u32 to silence this warning.

Fixes: 7f866986 ("leds: add PM8058 LEDs driver")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Lee Jones <lee.jones@linaro.org>