platform: msm: fix PFT when using direct-io

When read/write a file using dircet-io (O_DIRECT),
we can't get the inode from a bio by walking the path
bio->bi_io_vec->bv_page->mapping->host
since the page is anonymous and not mapped.
On the other more typical cases when not using O_DIRECT,
the page cache is used and the bv_page is available.

Change-Id: I349cad54a978ed9919f960d55f0f95c1e53262e5
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>