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

[ Upstream commit 6e785302dad32228819d8066e5376acd15d0e6ba ]

Missing a dependency.  Shouldn't show cifs posix extensions
in Kconfig if CONFIG_CIFS_ALLOW_INSECURE_DIALECTS (ie SMB1
protocol) is disabled.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>