cirrus: avoid write only variables

Compiling with GCC 4.6.0 20100925 produced a lot of warnings like:
In file included from /src/qemu/hw/cirrus_vga_rop.h:174:0,
                 from /src/qemu/hw/cirrus_vga.c:284:
/src/qemu/hw/cirrus_vga_rop2.h: In function 'cirrus_patternfill_0_8':
/src/qemu/hw/cirrus_vga_rop2.h:48:18: error: variable 'col' set but not used [-Werror=unused-but-set-variable]
/src/qemu/hw/cirrus_vga_rop2.h: In function 'cirrus_colorexpand_transp_0_8':
/src/qemu/hw/cirrus_vga_rop2.h:104:18: error: variable 'col' set but not used [-Werror=unused-but-set-variable]

Fix the warnings by introducing an inline function, which avoids
exposing write-only variables.

Signed-off-by: Blue Swirl <[email protected]>
diff --git a/hw/cirrus_vga_rop2.h b/hw/cirrus_vga_rop2.h
index 81a5b39..d28bcc6 100644
--- a/hw/cirrus_vga_rop2.h
+++ b/hw/cirrus_vga_rop2.h
@@ -23,15 +23,15 @@
  */
 
 #if DEPTH == 8
-#define PUTPIXEL()    ROP_OP(d[0], col)
+#define PUTPIXEL()    ROP_OP(&d[0], col)
 #elif DEPTH == 16
-#define PUTPIXEL()    ROP_OP(((uint16_t *)d)[0], col);
+#define PUTPIXEL()    ROP_OP_16((uint16_t *)&d[0], col)
 #elif DEPTH == 24
-#define PUTPIXEL()    ROP_OP(d[0], col); \
-                      ROP_OP(d[1], (col >> 8)); \
-                      ROP_OP(d[2], (col >> 16))
+#define PUTPIXEL()    ROP_OP(&d[0], col);        \
+                      ROP_OP(&d[1], (col >> 8)); \
+                      ROP_OP(&d[2], (col >> 16))
 #elif DEPTH == 32
-#define PUTPIXEL()    ROP_OP(((uint32_t *)d)[0], col)
+#define PUTPIXEL()    ROP_OP_32(((uint32_t *)&d[0]), col)
 #else
 #error unsupported DEPTH
 #endif