Revert "ecryptfs: forbid opening files without mmap handler"

Revert "ecryptfs: forbid opening files without mmap handler"

This reverts commit UEK4 e06914f2e9ac6b3f19d4461cb24b401f77ce4f17
which was based on mainline v4.7 commit:
2f36db71009304b3f0b95afacd8eba1f9f046b87
ecryptfs: forbid opening files without mmap handler

2f36db71 was replaced by mainline v4.7 commit:
f0fe970df3838c202ef6c07a4c2b36838ef0a88b
ecryptfs: don't allow mmap when the lower fs doesn't support it
which follows in another commit.

Also see mainline 4.7 commit 78c4e172412de5d0456dc00d2b34050aa0b683b5
Revert "ecryptfs: forbid opening files without mmap handler"

Orabug: 24971905
CVE: CVE-2016-1583
Signed-off-by: Chuck Anderson <chuck.anderson@oracle.com>