because the allocation could fail from iommu_map_page(), and the volume
of this call could be huge which may generate a lot of serial console
output and cosumes all CPUs.
Fix it by silencing the warning in this call site, and there is still a
dev_err() later to notify the failure.
Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: Joerg Roedel <jroedel@suse.de>