Revert "ashmem: avoid deadlock between read and mmap calls"

This reverts commit 1da431a78e9a4f9dd3f448639334d24a294080ed.
Revert "Squashed update of kernel from 3.4.47 to 3.4.48"

This reverts commit e21a96294d4ca02ab111bf16a4e578ead4026590.
1024 kb as max.