mfd: arizona: Update several pdata members to unsigned

Device tree and ACPI primarily deal with unsigned ints, many of the
pdata members in the Arizona driver are signed ints but are only ever
assigned positive values. Changing these pdata fields to unsigned ints
avoids us having to choose between overly verbose code and Sparse
warnings.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>