[media] media: davinci: vpbe: missing clk_put

we are getting struct clk using clk_get before calling
clk_prepare_enable. but if clk_prepare_enable fails, then we are
jumping to fail_mutex_unlock where we are just unlocking the mutex,
but we are not freeing the clock source.
this patch just adds a call to clk_put before jumping to
fail_mutex_unlock.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>