fs/ntfs3: Add iocharset= mount option as alias for nls=

Other fs drivers are using iocharset= mount option for specifying charset.
So add it also for ntfs3 and mark old nls= mount option as deprecated.

Reviewed-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>