npu: reword "error" to indicate it's actually a warning
npu: reword "error" to indicate it's actually a warning

Confirmed with Alistair on IRC, and earlier discussions with Russell.

Basically, I was a bit of an idiot and didn't think hard enough before
adding the FWTS annotation.

Without this patch, you get spurious FirmWare Test Suite (FWTS) warnings
about NVLink not working on machines that aren't fully populated with
GPUs.

Fixes: 00e3e275344a42f6a682be72c88c015df87a0e28
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

shenki/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,mikey/skiboot,legoater/skiboot,shenki/skiboot,qemu/skiboot,qemu/skiboot,mikey/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,open-power/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,open-power/skiboot,stewart-ibm/skiboot