ANDROID: Refactor fs readpage/write tracepoints.

Refactor the fs readpage/write tracepoints to move the
inode->path lookup outside the tracepoint code, and pass a pointer
to the path into the tracepoint code instead. This is necessary
because the tracepoint code runs non-preemptible. Thanks to
Trilok Soni for catching this in 4.4.

Change-Id: I7486c5947918d155a30c61d6b9cd5027cf8fbe15
Git-commit: d854b688
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Mohan Srinivasan <srmohan@google.com>
Signed-off-by: Runmin Wang <runminw@codeaurora.org>