sdm: hwc2 : Correcting the display Index handling

The display index for the virtual display, when
there is no virtual display attached, is
returned as -1 into uint64_t. Which makes
it out of bound for the hwc_display_.

Change-Id: Icbcc6ae013a98008abcaea6c5a44c4191d8b9456
Signed-off-by: satbir singh <satbsing@codeaurora.org>
1 file changed