cec: Fix runtime BUG when (CONFIG_RC_CORE && !CEC_CAP_RC)

cec: Fix runtime BUG when (CONFIG_RC_CORE && !CEC_CAP_RC)

commit 43c0c03961d0b19bd225a336897606b46e0021a6 upstream.

Currently when the RC Core is enabled (reachable) core code located
in cec_register_adapter() attempts to populate the RC structure with
a pointer to the 'parent' passed in by the caller.

Unfortunately if the caller did not specify RC capability when calling
cec_allocate_adapter(), then there will be no RC structure to populate.

This causes a "NULL pointer dereference" error.

Fixes: f51e80804f0 ("[media] cec: pass parent device in register(), not allocate()")
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>