util/grub-install: mips64el-efi: rename removable executable

as loongson3 machines with 64-bit EFI only accept BOOTMIPS.EFI

Author: chenx97

util/grub-install.c

@@ -1293,7 +1293,7 @@ main (int argc, char *argv[])
 	      efi_file = "BOOTRISCV64.EFI";
 	      break;
 	    case GRUB_INSTALL_PLATFORM_MIPS64EL_EFI:
-	      efi_file = "BOOTMIPS64EL.EFI";
+	      efi_file = "BOOTMIPS.EFI";
 	      break;
 	    default:
 	      grub_util_error ("%s", _("You've found a bug"));