hw/ppc/mac.h: remove unused BIOS_FILENAME definition

This definition has been moved to prep.c.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/hw/ppc/mac.h b/hw/ppc/mac.h
index 1e578dd..c1faf9c 100644
--- a/hw/ppc/mac.h
+++ b/hw/ppc/mac.h
@@ -34,7 +34,6 @@
 #define MAX_CPUS 1
 
 #define BIOS_SIZE     (1024 * 1024)
-#define BIOS_FILENAME "ppc_rom.bin"
 #define NVRAM_SIZE        0x2000
 #define PROM_FILENAME    "openbios-ppc"
 #define PROM_ADDR         0xfff00000