gralloc: Add owners for libgralloctypes

This library is already merged in internal master. This patch adds
the OWNERS file. This patch must be merged into AOSP master because
AOSP contains the source of truth for every owners file.

Bug: 135140280
Test: Compiles
Change-Id: Ibb32d7655cafae8a875c07ee4b686501460d6d66
1 file changed