Remove forward declaration of non-existant variable

This variable has been removed 5 years ago in 970ac5a3082428dca91171f270dcd95d6f4b2636.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

include/sysemu/sysemu.h

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 1d9599e..ae49088 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -94,7 +94,6 @@
 } DisplayType;
 
 extern int autostart;
-extern int bios_size;
 
 typedef enum {
     VGA_NONE, VGA_STD, VGA_CIRRUS, VGA_VMWARE, VGA_XENFB, VGA_QXL,