octeontx2-pf: select CONFIG_NET_DEVLINK

The octeontx2 pf nic driver failsz to link when the devlink support
is not reachable:

aarch64-linux-ld: drivers/net/ethernet/marvell/octeontx2/nic/otx2_devlink.o: in function `otx2_dl_mcam_count_get':
otx2_devlink.c:(.text+0x10): undefined reference to `devlink_priv'
aarch64-linux-ld: drivers/net/ethernet/marvell/octeontx2/nic/otx2_devlink.o: in function `otx2_dl_mcam_count_validate':
otx2_devlink.c:(.text+0x50): undefined reference to `devlink_priv'
aarch64-linux-ld: drivers/net/ethernet/marvell/octeontx2/nic/otx2_devlink.o: in function `otx2_dl_mcam_count_set':
otx2_devlink.c:(.text+0xd0): undefined reference to `devlink_priv'
aarch64-linux-ld: drivers/net/ethernet/marvell/octeontx2/nic/otx2_devlink.o: in function `otx2_devlink_info_get':
otx2_devlink.c:(.text+0x150): undefined reference to `devlink_priv'

This is already selected by the admin function driver, but not the
actual nic, which might be built-in when the af driver is not.

Fixes: 2da48943 ("octeontx2-pf: devlink params support to set mcam entry count")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>