[cloud] Show CPU vendor and model in example cloud boot scripts

Some problems arise only when running on a specific CPU type (e.g.
non-functional timer interrupts as observed in Azure AMD instances).
Include the CPU vendor and model within the sample cloud boot scripts,
to assist in debugging such problems.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/config/cloud/aws.ipxe

 #!ipxe
 
 echo Amazon EC2 - iPXE boot via user-data
+echo CPU: ${cpuvendor} ${cpumodel}
 ifstat ||
 dhcp ||
 route ||

src/config/cloud/gce.ipxe

 #!ipxe
 
 echo Google Compute Engine - iPXE boot via metadata
+echo CPU: ${cpuvendor} ${cpumodel}
 ifstat ||
 dhcp ||
 route ||

src/config/cloud/settings.h

+/* It can often be useful to know the CPU on which a cloud instance is
+ * running (e.g. to isolate problems with Azure AMD instances).
+ */
+#define CPUID_SETTINGS