hotplug_mem_negative:Update ipa limit search criteria

Update ipa limit search criteria

Signed-off-by: zhenyzha <[email protected]>

qemu/tests/cfg/hotplug_mem_negative.cfg

@@ -25,7 +25,7 @@
                 # On arm64, machine type can be used to request the
                 # physical address size for the VM. For backward compatibility,
                 # the default IPA size is 40bits.
-                ipa_limit_check = "cat /var/log/messages | grep "IPA Size Limit:" | awk '{print $11}'"
+                ipa_limit_check = "grep 'IPA Size Limit:' /var/log/messages | head -n 1 | awk '{print $(NF-1)}'"
                 # Start address of system memory is 1G.
                 system_init_mem = 1
                 RHEL.8: