Revert "scatterlist: use sg_phys()"

commit db0fa0cb "scatterlist: use sg_phys()" did replacements of
the form:

    phys_addr_t phys = page_to_phys(sg_page(s));
    phys_addr_t phys = sg_phys(s) & PAGE_MASK;

However, this breaks platforms where sizeof(phys_addr_t) >
sizeof(unsigned long).  Revert for 4.3 and 4.4 to make room for a
combined helper in 4.5.

Cc: <stable@vger.kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: db0fa0cb

 ("scatterlist: use sg_phys()")
Suggested-by: Joerg Roedel <joro@8bytes.org>
Reported-by: Vitaly Lavrov <vel21ripn@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>