cirrus: fix an uninitialized variable

Noticed by paying attention to a compiler warning (reported for the
only caller of the function modified, vga_ioport_read()).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/hw/cirrus_vga.c
+++ b/hw/cirrus_vga.c
@@ -1658,8 +1658,8 @@ cirrus_hook_read_cr(CirrusVGAState * s, 
     default:
 #ifdef DEBUG_CIRRUS
 	printf("cirrus: inport cr_index %02x\n", reg_index);
-	*reg_value = 0xff;
 #endif
+	*reg_value = 0xff;
 	break;
     }