remap_file_pages: remove since corresponding syscall is depricated

To be replaced with emulation in upcoming kernel (3.18 or 3.19).
http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/mm?id=05ee1456de118f0cac2a99fa35418be48c9182f8

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>