package/btrfs-progs: bump version to 5.6

package/btrfs-progs: bump version to 5.6

Changelog:
https://btrfs.wiki.kernel.org/index.php/Changelog#By_version_.28btrfs-progs.29

Removed patches applied upstream:
https://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git/commit/?id=9a03f6d41f8e6b3312dc0c87563d8dbd10eafafe
https://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git/commit/?id=4b3e22e988c26c6c814f9ad3f50f493cd4d9dd2a

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>