The svc_create_memory_pool() function returns error pointers.  It never
returns NULL.  Fix the check.

Fixes: 7ca5ce89 ("firmware: add Intel Stratix10 service layer driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/5f9a8cb4-5a4f-460b-9cdc-2fae6c5b7922@kili.mountainSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>