gralloc: Fix issue with mmap/munmap meta due to reserved size am: c9a0d7b113 am: eedb45ab30 am: 58137990bb

Original change: https://googleplex-android-review.googlesource.com/c/platform/hardware/qcom/sm8150/display/+/19355927

Change-Id: Ie36a537022c3c6733f27bbd943ed9e74dddd10c9
Signed-off-by: Automerger Merge Worker <[email protected]>