fs: get_acl() must be allowed to return EOPNOTSUPP

fs: get_acl() must be allowed to return EOPNOTSUPP

posix_acl_xattr_get requires get_acl() to return EOPNOTSUPP if the
filesystem cannot support acls. This is needed for NFS, which can't
know whether or not the server supports acls until it tries to get/set
one.
This patch converts posix_acl_chmod and posix_acl_create to deal with
EOPNOTSUPP return values from get_acl().

Reported-by: Russell King <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Cc: Al Viro [email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Tested-by: Takashi Iwai <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>