regmap: cache: set max_register with reg_stride

Current logic does not consider multi-stride cases,
the max_register have to calculate with reg_stride
because it is a kind of address range.

Signed-off-by: Jeongtae Park <jtp.park@samsung.com>
Link: https://lore.kernel.org/r/20220425114613.15934-1-jtp.park@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org>