arm: add support for LZ4-compressed kernels

This patch integrates the LZ4 decompression code to the arm pre-boot code.
And it depends on two patchs below

lib: add support for LZ4-compressed kernels
decompressors: add lz4 decompressor module

Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com>

Conflicts:
	arch/arm/boot/compressed/Makefile