mtd: rawnand: All AC chips have a broken GET_FEATURES(TIMINGS).

Make sure we flag all broken chips as not supporting this feature.
Also move this logic to a new function to keep things readable.

Fixes: 34c5c01e ("mtd: rawnand: macronix: nack the support of changing timings for one chip")
Cc: <stable@vger.kernel.org>
Signed-off-by: Mason Yang <masonccyang@mxic.com.tw>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>