modesetting: Add the "DPI" connector type.

The number for it was merged to drm_mode.h in kernel 4.7, and the
output_names[] array just requires that we slot in new strings in
order.

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

hw/xfree86/drivers/modesetting/drmmode_display.c

@@ -1621,6 +1621,7 @@ static const char *const output_names[] = {
     "eDP",
     "Virtual",
     "DSI",
+    "DPI",
 };
 
 static xf86OutputPtr find_output(ScrnInfoPtr pScrn, int id)