ARM: shmobile: r8a7790: add audio clock

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 old/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>