[media] cec: Add cec_get_drvdata()

Add a helper function to get driver private data from CEC
adapter. This helps the readability a little bit and allows
to change the 'priv' field name to something else without
needing to touch all drivers.

Change-Id: I280a4e203b4918c5bc194e3618d9733d8c8fb175
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Git-commit: 0b0b97dcc79fe2b34d320805c4389d87980a0e51
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Venkata Prahlad Valluru <vvalluru@codeaurora.org>