mfd: tps65910: Rid data size incompatibility warn when building for 64bit

Extinguishes:

../drivers/mfd/tps65910.c: In function ‘tps65910_parse_dt’:
../drivers/mfd/tps65910.c:404:14:
	warning: cast from pointer to integer of different size

Signed-off-by: Lee Jones <lee.jones@linaro.org>