cirrus: fix PUTPIXEL macro

Should be "c" not "col".  The macro is used with "col" as third parameter
everywhere, so this tyops doesn't break something.

Fixes: 026aeffcb4752054830ba203020ed6eb05bcaba8
Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 1490168303-24588-1-git-send-email-kraxel@redhat.com

hw/display/cirrus_vga_rop2.h

@@ -29,8 +29,8 @@
 #elif DEPTH == 24
 #define PUTPIXEL(s, a, c)    do {          \
         ROP_OP(s, a,     c);               \
-        ROP_OP(s, a + 1, (col >> 8));      \
-        ROP_OP(s, a + 2, (col >> 16));     \
+        ROP_OP(s, a + 1, (c >> 8));        \
+        ROP_OP(s, a + 2, (c >> 16));       \
     } while (0)
 #elif DEPTH == 32
 #define PUTPIXEL(s, a, c)    ROP_OP_32(s, a, c)