ARM: multi_v7_defconfig: ti: Enable networking options for nfs boot

Enable networking options required for NFS boot on TI platforms, which is
widely for automated test systems.
- enable new TI CPSW switch driver and related NET_SWITCHDEV config
- enable TI DP83867 phy
- explicitly enable PTP clock support to ensure dependent networking
drivers will stay built-in.

vmlinux size changes:
- before:
   text       data        bss        dec        hex    filename
14703736    8024602     444976    23173314    16198c2    ./omap-arm/vmlinux

- after:
   text       data        bss        dec        hex    filename
14727271    8029150     444528    23200949    16204b5    ./omap-arm/vmlinux

diff: 27635 (dec)

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Nishanth Menon <nm@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20201030124650.20349-1-grygorii.strashko@ti.com

'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>