variable hint size WIP
dm-cache-policy-hints: new + add dm_cache_policy_set_hint_size() to support it
dm-cache-metadata.c: fix missing policy_hint_size stored in superblock
dm-cache-policy-hints.c: optimize using macros for endianess conversion of hints values
dm-cache-policy-hints: free hints_buffer on destroy
dm-cache-mezadata.c: address hint vaue buffer FIXME:
dm-cache-policy-hints.c: fix loop in __hint_xfer_disk()
dm-cache-policy-internal.h: drop max hint size to 256 bytes
dm-cache-policy-hints.c: fix typo. remove superfluous conditional in free_hash()
Merge remote-tracking branch 'github-heinz/heinz-variable-hint-size' into cache-coherency-changes
[dm-cache] remove some cruft from Kconfig and Makefile that Heinz accidentally introduced