hwc2 : Correcting primary display count handling

Check the count for the pluggable (max_pluggable)
and buildin display (max_buildin) to be non-zero
before reducing the count for the instance of
primary display already used.

Signed-off-by: satbir singh <satbsing@codeaurora.org>

Change-Id: Ie067badd523d9ea9db428de596a8cc2e7e2e26e8
1 file changed