CVE-2022-49510

In the Linux kernel, the following vulnerability has been resolved:

drm/omap: fix NULL but dereferenced coccicheck error

Fix the following coccicheck warning:
./drivers/gpu/drm/omapdrm/omap_overlay.c:89:22-25: ERROR: r_ovl is NULL
but dereferenced.

Here should be ovl->idx rather than r_ovl->idx.