ioemu: drop unused shared_vram variable

diff -r 341750d68c38 tools/ioemu/hw/cirrus_vga.c
@@ -281,8 +281,6 @@
 
 static uint8_t rop_to_index[256];
     
-void *shared_vram;
-
 /***************************************
  *
  *  prototypes.

diff -r 341750d68c38 tools/ioemu/vl.h
@@ -153,8 +153,6 @@
                      unsigned int address_bits, unsigned long *extent_start);
 int set_mm_mapping(int xc_handle, uint32_t domid, unsigned long nr_pages,
                    unsigned int address_bits, unsigned long *extent_start);
-
-extern void *shared_vram;
 
 extern FILE *logfile;