[SCSI] Fix Ultrastor asm snippet

Commit 1292500b replaced

"=m" (*field) : "1" (*field)

with

"=m" (*field) :

with comment "The following patch fixes it by using the '+' operator on
the (*field) operand, marking it as read-write to gcc."
'+' was actually forgotten.  This really puts it.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: stable@kernel.org
Signed-off-by: James Bottomley <jbottomley@parallels.com>

drivers/scsi/ultrastor.c

@@ -307,7 +307,7 @@ static inline int find_and_clear_bit_16(unsigned long *field)
 	"0: bsfw %1,%w0\n\t"
 	"btr %0,%1\n\t"
 	"jnc 0b"
-	: "=&r" (rv), "=m" (*field) :);
+	: "=&r" (rv), "+m" (*field) :);
 
   return rv;
 }