Add buffer length check for XTRA data

To prevent reading beyond the length of
the buffer that contains XTRA data, a
check has been introduced assuming an
approximate limit for the size of the
data

Change-Id: I7e05beadec76c3308448b9198fd23c8e8b97394d
jflte: increase read ahead cache earlier

Change-Id: Iebe91d2586fbaf692b4e6d8759c34fc5e30aab7d