xfs: disambiguate units for ftrace fields tagged "count"

Some of our tracepoints have a field known as "count".  That name
doesn't describe any units, which makes the fields not very useful.
Rename the fields to capture units and ensure the format is hexadecimal
when we're referring to blocks, extents, or IO operations.

"fsbcount" are in units of fs blocks
"bytecount" are in units of bytes

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>