hwc2: Use GRALLOC1_PFN_ALLOCATE to allocate buffer

1. Define gralloc1 function pointers needed to allocate buffer
2. Use the gralloc1 function pointers to allocate buffer instead of
   perform function to avoid any synchronization issues.
3. Remove functionality to allocate buffer from perform function

Change-Id: If686181409a179d3d911dfbd0f0c0eab7a7ffa99
CRs-Fixed: 2115331
5 files changed