net: dpaa_eth: remove dead select in menuconfig FSL_DPAA_ETH

The menuconfig FSL_DPAA_ETH selects config FSL_FMAN_MAC, but the config
FSL_FMAN_MAC never existed in the kernel tree.

Hence, ./scripts/checkkconfigsymbols.py warns:

FSL_FMAN_MAC
Referencing files: drivers/net/ethernet/freescale/dpaa/Kconfig

Remove this dead select in menuconfig FSL_DPAA_ETH.

Fixes: 9ad1a374 ("dpaa_eth: add support for DPAA Ethernet")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>