hugetlbfs: fix alignment of huge page requests

When calling shmget() with SHM_HUGETLB, shmget aligns the request size to
PAGE_SIZE, but this is not sufficient.

Modify hugetlb_file_setup() to align requests to the huge page size, and
to accept an address argument so that all alignment checks can be
performed in hugetlb_file_setup(), rather than in its callers.  Change
newseg() and mmap_pgoff() to match the new prototype and eliminate a now
redundant alignment check.

[akpm@linux-foundation.org: fix build]
Signed-off-by: Steven Truelove <steven.truelove@utoronto.ca>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>