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

Extinguishes:

../drivers/mfd/arizona-core.c: In function ‘arizona_of_get_type’:
../drivers/mfd/arizona-core.c:505:10:
	warning: cast from pointer to integer of different size

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