off_t is problematic for use as a file/block offset: it is signed, and
on 32-bit platforms, it can be 32 bits (depending on the settings of
_FILE_OFFSET_BITS and _LARGEFILE_SOURCE).
The blockdev layer already uses uint64_t to represent offsets; replace
the blockdev module uses of off_t in internal functions with uint64_t
to match.
Change-Id: I77a2e594572c56f1cd8a7a080f985ea5b27c35f3
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>