Replace android.hidl.allocator usage

Allocate the memory directly with ashmem_create_region which is what the
allocator implementation does.
The HIDL allocator service is no longer installed on a new devices with
the deprecation of HIDL.

Test: atest Mpeg2tsUnitTest
Bug: 205764958
Change-Id: I34a96ac63e0be9fb81d281d3bdab22146fd1c3cd