x86/efi: add FAT32 esp mounting support

Adds a new function get_magic_fat32() in base-files to read FAT32 magic.
Now FAT32 EFI system partition can be handled in the same way as FAT12/FAT16.

Signed-off-by: Kagurazaka Kotori <kagurazakakotori@gmail.com>
[replace '-o' with '] || [' to satisfy shellsheck]
Signed-off-by: Paul Spooren <mail@aparcar.org>

package/base-files/files/lib/upgrade/common.sh

@@ -133,14 +133,19 @@ get_magic_vfat() {
 	(get_image "$@" | dd bs=1 count=3 skip=54) 2>/dev/null
 }
 
+get_magic_fat32() {
+	(get_image "$@" | dd bs=1 count=5 skip=82) 2>/dev/null
+}
+
 part_magic_efi() {
 	local magic=$(get_magic_gpt "$@")
 	[ "$magic" = "EFI PART" ]
 }
 
 part_magic_fat() {
 	local magic=$(get_magic_vfat "$@")
-	[ "$magic" = "FAT" ]
+	local magic_fat32=$(get_magic_fat32 "$@")
+	[ "$magic" = "FAT" ] || [ "$magic_fat32" = "FAT32" ]
 }
 
 export_bootdevice() {