VFS: Remove redundant open-coded mode bit checks in open_exec().

The check in open_exec() for inode->i_mode & 0111 has been made
redundant by the fix to permission().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
(cherry picked from 1d3741c5d991686699f100b65b9956f7ee7ae0ae commit)