dpaa2-eth: Fix Kconfig dependencies

Both ARCH_LAYERSCAPE and COMPILE_TEST dependencies are already implied
through the FSL_MC_BUS dep, so there's no need to state it explicitly.

Also, the fsl-mc bus depends on COMPILE_TEST only for some
architectures (arm, arm64, ppc, x86), so it's not correct to
claim build support unconditionally.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>