mfd: rsmu: Support 32-bit address space

We used to assume 0x2010xxxx address. Now that we need to access
0x2011xxxx address, we need to support read/write the whole 32-bit
address space.

Also defined RSMU_MAX_WRITE_COUNT and RSMU_MAX_READ_COUNT for readability

Signed-off-by: Min Li <min.li.xe@renesas.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/MW5PR03MB693295AF31ABCAF6AE52EE74A08B9@MW5PR03MB6932.namprd03.prod.outlook.com