drop create= from mount options (v2)

Otherwise mount may return -EINVAL if in-kernel super-block parser
objects (as is the case with ext4).

Changelog v2:
	also drop 'optional'
	specifically drop create=dir, not create=*
	fix order of arguments for memmove

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>