Update config/grub/config/grub.cfg

grub.cfg: add BTRFS subvol support

config/grub/config/grub.cfg

@@ -46,7 +46,9 @@ fi
 
 function try_user_config {
 	set root="${1}"
-	for dir in boot grub grub2 boot/grub boot/grub2; do
+
+	# The @/... entries are for cases where the BTRFS filesystem is being used
+	for dir in boot grub grub2 boot/grub boot/grub2 @/boot @/grub @/grub2 @/boot/grub @/boot/grub2; do
 		for name in '' osboot_ autoboot_ libreboot_ coreboot_; do
 			if [ -f /"${dir}"/"${name}"grub.cfg ]; then
 				unset superusers