From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Get rid of the sentinel in forced_comnectors[] and just
use ARRAY_SIZE() to determine the limits.

The sentinel stuff actually looks broken due to the use of
ARRAY_SIZE() in forced_connector_free_index(), which was
apparently my doing in
commit ed6539ced33e ("lib/igt_kms: Rework forced connector handling")

Cc: Kunal Joshi <kunal1.joshi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>