mtd: rawnand: ams-delta: Drop useless local variable

For consistency with adjacent code patterns used in the driver probe
function, store data GPIO array pointer directly in a respective field
of the driver private structure instead of storing it intermediately
in a local variable for error checking.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200212003929.6682-13-jmkrzyszt@gmail.com