bcache.h: add BCH_FEATURE_INCOMPAT_LARGE_BUCKET to BCH_FEATURE_INCOMPAT_SUPP

BCH_FEATURE_INCOMPAT_LARGE_BUCKET is a feature to support 32bits bucket
size, which is incompatible feature for existing on-disk layout. This
patch adds this feature bit to BCH_FEATURE_INCOMPAT_SUPP feature set.

Signed-off-by: Coly Li <colyli@suse.de>