Speed up boot time. Raised read ahead page cache size to 2048 x2 (=4096)

Change-Id: Ie652283d403f8d22cb38270d68f34821d958a4b8
Merge https://github.com/TeamFahQ/msm8660-common_lz_kernel into HEAD
Undoing changes for cm-10.1 merge

Change-Id: Ic3ca59c263bf79facf209ca2cd85ec9afc780547