regmap: Support paging for buses with reg_read()/reg_write()

We don't currently support paging for regmaps where the I/O happens through
bus provided reg_read() and reg_write() operatons, we simply ignore the
range since nothing is wired up properly. Wire things up.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230324-regmap-reg-read-write-page-v1-1-1fbc0dac67ae@kernel.org