Add CONFIG_BIOSEMU define to guard all the bios emulator code

Signed-off-by: Jason Jin <Jason.jin@freescale.com>

This patch fix the compile issue on the board that did not enable the bios emulator
diff --git a/drivers/bios_emulator/x86emu/prim_ops.c b/drivers/bios_emulator/x86emu/prim_ops.c
index e0827d7..c1152ea 100644
--- a/drivers/bios_emulator/x86emu/prim_ops.c
+++ b/drivers/bios_emulator/x86emu/prim_ops.c
@@ -100,6 +100,8 @@
 #define PRIM_OPS_NO_REDEFINE_ASM
 #include "x86emu/x86emui.h"
 
+#if defined(CONFIG_BIOSEMU)
+
 /*------------------------- Global Variables ------------------------------*/
 
 static u32 x86emu_parity_tab[8] =
@@ -2443,3 +2445,5 @@
     M.x86.R_SP += 4;
     return res;
 }
+
+#endif