xen/x86: use INFO level for node's without memory log message

xen/x86: use INFO level for node's without memory log message

In previous code, Xen was using KERN_WARNING for log message
when Xen found a node without memory. Xen will print this
warning message, and said that this may be an BIOS Bug or
mis-configured hardware. But actually, this warning is bogus,
because in an NUMA setting, nodes can only have processors,
and with 0 bytes memory. So it is unreasonable to warn about
BIOS or hardware corruption based on the detection of node
with 0 bytes memory.

So in this patch, we remove the warning messages, but just
keep an info message to info users that there is one or more
nodes with 0 bytes memory in the system.

Signed-off-by: Wei Chen <wei.chen@arm.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>