ARM: shmobile: r8a7778: add audio clock in new style

Current audio clock doesn't have dependency to device/driver,
but, it is not good design for DT support.
To avoid branch merge conflict issue,
it uses this load map, and this patch is 1) part.
 1) add new style clock in platform
 2) add new style clock method in driver
 3) remove old tyle clock from platform

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>