arm64: defconfig: compile ak4613 and renesas sound as modules

Compile the renesas sound and ak4613 drivers as modules to reduce the ARM64
kernel size. These modules are currently only used by Renesas platforms so
there should little risk of negative impact of this change on other users.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
[simon: consolidated two patches into one]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>