Fix typo in marvell octeontx2 documentation

Documentation/networking/device_drivers/ethernet/marvell/octeontx2.rst
Fixes a spelling mistake: "funcionality" → "functionality".

Signed-off-by: Faisal Bukhari <faisalbukhari523@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>