The max_register setting for ak4642, ak4643 and ak4648 are wrong, fix it.

According to the datasheet:
        the maximum valid register for ak4642 is 0x1f
        the maximum valid register for ak4643 is 0x24
        the maximum valid register for ak4648 is 0x27

The default settings for ak4642 and ak4643 are the same for 0x0 ~ 0x1f
registers, so it's fine to use the same reg_default table with differnt
num_reg_defaults setting.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Tested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>