grub: no biosdisk for mips arc

package/grub/Makefile

@@ -43,7 +43,7 @@ GRUB_DIR=		boot/grub
 GRUB_PREFIX=		(hd0,msdos1)/boot/grub
 GRUB_TARGET=		mips
 GRUB_PLATFORM=		arc
-GRUB_MODULES=		boot linux ext2 fat part_msdos part_gpt normal biosdisk
+GRUB_MODULES=		boot linux ext2 fat part_msdos part_gpt normal
 endif
 
 ifeq ($(ADK_PACKAGE_GRUB_PC),y)