Add khushalsagar@ to gpu/OWNERS

Change-Id: Ic12f69ef4d4ba6c9fe02217ad6912175550cd8a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2028631
Auto-Submit: Eric Karl <ericrk@chromium.org>
Commit-Queue: Khushal <khushalsagar@chromium.org>
Reviewed-by: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736573}

gpu/OWNERS

 backer@chromium.org
 ericrk@chromium.org
 kbr@chromium.org
+khushalsagar@chromium.org
 vmiura@chromium.org
 zmo@chromium.org
 sunnyps@chromium.org