aufs: bugfix, stop calling security_mmap_file() again

Actually this commit is a revival of
	a1d9363 2012-06-08 aufs: for 3.5-rcN, security_mmap_file()
That commit was reverted after a discussion. For details, see these.
	6608a07 2012-07-29 aufs: aufs_mmap() calls security_mmap_file() directly
	66ecc70 2012-07-24 Revert "aufs: cosmetics for aufs_mmap()"
	7573c5b 2012-07-24 Revert "aufs: for 3.5-rcN, new au_security_file_mmap() 1/2"
	c3a3e02 2012-07-24 Revert "aufs: for 3.5-rcN, call au_security_file_mmap() 2/2"
	ad02614 2012-06-13 aufs: for 3.5-rcN, call au_security_file_mmap() 2/2
	aa29a06 2012-06-13 aufs: for 3.5-rcN, new au_security_file_mmap() 1/2
	b028c62 2012-06-08 aufs: cosmetics for aufs_mmap()

The real problem is reported and I decided to stop calling
security_mmap_file() for the branch-fs file from aufs_mmap() again.

See: http://www.mail-archive.com/aufs-users@lists.sourceforge.net/msg04609.html
Reported-by: Matthew Riley <mdriley@gmail.com>
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
Merge "aufs: bugfix, stop calling security_mmap_file() again" into distrotech-linux-3.14