ARM: OMAP4+: Cleanup the clocks layer

Currently there is quite a lot of code which
is duplicated in the clocks code for OMAP 4 and 5
Socs. Avoiding this here by moving the clocks
data to a SOC specific place and the sharing the
common code.

This helps in addition of a new Soc with minimal
changes.

Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@ti.com>