It will cause null-ptr-deref if platform_get_resource_byname() returns NULL,
we need check the return value.

Fixes: 858e26a5 ("spi: spi-fsl-qspi: Reduce devm_ioremap size to 4 times AHB buffer size")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220505093954.1285615-1-yangyingliang@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>