xz: fix spelling in comments

xz: fix spelling in comments

uncompressible -> incompressible
non-splitted -> non-split

Link: https://lore.kernel.org/r/20211010213145.17462-6-xiang@kernel.org
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 0a434e0a2c9f
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>