net: mscc: Add SPDX identifier

ocelot_qsys.h is missing the SPDX identfier, fix that.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Allan W. Nielsen <allan.nielsen@microsemi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>