CEC needs the source physical address. Parsing it is trivial with the
existing EDID CEA DB infrastructure.

Default to CEC_PHYS_ADDR_INVALID (0xffff) instead of 0 to cater for
easier CEC usage.

Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: linux-media@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/8c6b6403932536b6849e0b44e1ee6e7ebdbe4a69.1692884619.git.jani.nikula@intel.com