devlink: report cell size

devlink: report cell size

Print the value of DEVLINK_ATTR_SB_POOL_CELL_SIZE, if reported.

Example:
pci/0000:82:00.0:
  sb 1 pool 0 type egress size 40945664 thtype static cell_size 2048
  sb 2 pool 0 type egress size 258867200 thtype static cell_size 10240
...

v3: - don't double space.
v2: - fix spelling.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>