mtd: rawnand: gpmi: return valid value from bch_set_geometry()

The caller of bch_set_geometry() expects the return value to
be an error code, so !0 is not valid. return the error from the
just called function instead.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>