decompressors: make the default XZ_DEC_* config match the selected architecture

decompressors: make the default XZ_DEC_* config match the selected architecture

Change the defautl XZ_DEC_* config symbol to match the configured
architecture.  It is perfectly legitimate to support multiple XZ BCJ
filters for different architectures (e.g.: to mount foreign squashfs/xz
compressed filesystems), it is however more natural not to select them all
by default, but only the one matching the configured architecture.

Signed-off-by: Florian Fainelli <[email protected]>
Acked-by: Lasse Collin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>