[media] media:davinci: clk - {prepare/unprepare} for common clk

As a first step towards migrating davinci platforms to use common clock
framework, replace all instances of clk_enable() with clk_prepare_enable()
and clk_disable() with clk_disable_unprepare().
Also fixes some issues related to clk clean up in the driver

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Acked-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Tested-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>