mtd: nand: sunxi: Return on set_feature only when not ENOTSUPP

Return the error code of the set_features function only if
the error code is not ENOTSUPP. Otherwise, if this function
is not supported, it will return and fail to initialize the
NAND.

Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
Acked-by: Jagan Teki <jagan@openedev.com>