Revert "cifs: In Kconfig CONFIG_CIFS_POSIX needs depends on legacy (insecure cifs)"

This reverts commit 4cd37663 which is
commit 6e785302dad32228819d8066e5376acd15d0e6ba upstream.

Yi writes:
	I notice that 4.4.169 merged 60da90b224ba7 ("cifs: In Kconfig
	CONFIG_CIFS_POSIX needs depends on legacy (insecure cifs)") add
	a Kconfig dependency CIFS_ALLOW_INSECURE_LEGACY, which was not
	defined in 4.4 stable, so after this patch we are not able to
	enable CIFS_POSIX anymore. Linux 4.4 stable didn't merge the
	legacy dialects codes, so do we really need this patch for 4.4?

So revert this patch in 4.9 as well.

Reported-by: "zhangyi (F)" <yi.zhang@huawei.com>
Cc: Steve French <stfrench@microsoft.com>
Cc: Pavel Shilovsky <pshilov@microsoft.com>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>