net: airoha: Fix a NULL vs IS_ERR() bug in airoha_npu_run_firmware()

The devm_ioremap_resource() function returns error pointers.  It never
returns NULL.  Update the check to match.

Fixes: e27dba19 ("net: Use of_reserved_mem_region_to_resource{_byname}() for "memory-region"")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/fc6d194e-6bf5-49ca-bc77-3fdfda62c434@sabinyo.mountain


Signed-off-by: Jakub Kicinski <kuba@kernel.org>