checkpatch: Add QEMU specific rule

The new rule detects two wrong variants of QEMU.
It was tested with commit b5a8fe5e.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

scripts/checkpatch.pl

@@ -2849,6 +2849,11 @@ sub process {
 				ERROR("lockdep_no_validate class is reserved for device->mutex.\n" . $herecurr);
 			}
 		}
+
+# QEMU specific tests
+		if ($rawline =~ /\b(?:Qemu|QEmu)\b/) {
+			WARN("use QEMU instead of Qemu or QEmu\n" . $herecurr);
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on