mtd: denali_dt: Change return value to fix smatch warning
platform_get_irq() also returns -ENXIO upon failure.
Use it instead of hardcoded return type.
Fixes the following smatch warning:
drivers/mtd/nand/denali_dt.c:93 denali_dt_probe() info:
why not propagate 'denali->irq' from platform_get_irq() instead of (-6)?