net: ethernet: fs_enet: Add missing MODULE_LICENSE

[ Upstream commit 445c6198fe7be03b7d38e66fe8d4b3187bc251d4 ]

Since commit 1d6cd3929360 ("modpost: turn missing MODULE_LICENSE()
into error") the ppc32_allmodconfig build fails with:

  ERROR: modpost: missing MODULE_LICENSE() in drivers/net/ethernet/freescale/fs_enet/mii-fec.o
  ERROR: modpost: missing MODULE_LICENSE() in drivers/net/ethernet/freescale/fs_enet/mii-bitbang.o

Add the missing MODULE_LICENSEs to fix the build. Both files include a
copyright header indicating they are GPL v2.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>