Optimization for booting memtest86-usb.img.

INSTALL/grub/grub.cfg

@@ -2321,13 +2321,14 @@ function img_common_menuentry {
         ventoy_img_ubos
     elif [ -f (vtimghd,2)/etc/openwrt_version ]; then
         ventoy_img_openwrt    
-    elif [ -f (vtimghd,1)/efi/boot/mt86.png ]; then 
+    else
+        if [ -f (vtimghd,1)/efi/boot/mt86.png ]; then 
             if [ "$grub_platform" = "pc" ]; then
                 img_unsupport_tip
-        else
-            ventoy_img_memtest86            
             fi 
-    else
+        fi
+
+        #common chain
         vt_linux_chain_data "${vtoy_iso_part}${vt_chosen_path}"
         ventoy_acpi_param ${vtoy_chain_mem_addr} 512
         if [ "$grub_platform" = "pc" ]; then