mtd: rawnand: meson: check return value of devm_kasprintf()

mtd: rawnand: meson: check return value of devm_kasprintf()

[ Upstream commit 5a985960a4dd041c21dbe9956958c1633d2da706 ]

devm_kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure. Ensure the allocation was successful by
checking the pointer validity.

Fixes: 1e4d3ba66888 ("mtd: rawnand: meson: fix the clock")
Signed-off-by: Yi Yang <yiyang13@huawei.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20231019065548.318443-1-yiyang13@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>