Clear out the BiosTableSpace array on each boot.

This makes sure ctrl-alt-delete doesn't leave left over settings.
diff --git a/src/memmap.c b/src/memmap.c
index 1cc4691..c56f6f5 100644
--- a/src/memmap.c
+++ b/src/memmap.c
@@ -126,6 +126,7 @@
 void
 memmap_setup()
 {
+    memset(BiosTableSpace, 0, CONFIG_MAX_BIOSTABLE);
     bios_table_cur_addr = (u32)BiosTableSpace;
     bios_table_end_addr = bios_table_cur_addr + CONFIG_MAX_BIOSTABLE;
     dprintf(1, "bios_table_addr: 0x%08x end=0x%08x\n",