kernel-uboot: Support lzma compressed algorithm

kernel-uboot: Support lzma compressed algorithm

Linux kernel supports to compress its output binary with lzma algorithm and
U-Boot support to decompress lzma compressed image.

Both xz and lzma algorithms are identical and users can use xz utility with
format parameter to compress Image which supports lzma algorithm.

Add the following command to support lzma. This command is refer to Linux
kernel, https://github.com/torvalds/linux/blob/master/arch/powerpc/boot/wrapper

"xz --format=lzma -f -6 linux.bin"

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>