checkpatch: port fix from kernel "## is not a valid modifier"

checkpatch currently loops on fpu/softfloat.c
Turns out this is fixed in the Linux version of checkpatch.

So this is a port of Andy Whitcrofts fix from Linux,
Original commit was commit 89a883530fe7 ("checkpatch: ## is not a
valid modifier")

As suggested by Peter Maydell for the QEMU version we drop the last "|"
as there seems to be no need for that. (FWIW, the kernel discusion about
that dried out:
http://www.spinics.net/lists/kernel/msg1944421.html
)

Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <1444291524-66569-1-git-send-email-borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/checkpatch.pl

@@ -1010,7 +1010,9 @@ sub possible {
 			case|
 			else|
 			asm|__asm__|
-			do
+			do|
+			\#|
+			\#\#
 		)(?:\s|$)|
 		^(?:typedef|struct|enum)\b
 	    )}x;