configs: Fixup some CPSW-related items

- For am335x_pdu001 we do not want the CPSW driver, drop it
- Re-sync the defconfig for am43xx_evm_rtconly as it came in after the
  patch that converted CPSW to Kconfig was posted but before it was
  applied.
- Drop empty section / comments from pengwyn
- Drop empty section / comments from baltos and drop unused
  CONFIG_SPL_NET_VCI_STRING (it does not enable CONFIG_SPL_NET_SUPPORT
  currently and SPL_NET_VCI_STRING has been migrated already).

Cc: Felix Brack <fb@ltec.ch>
Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Lothar Felten <lothar.felten@gmail.com>
Fixes: f02b8d17 ("Migrate CONFIG_DRIVER_TI_CPSW to Kconfig")
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Felix Brack <fb@ltec.ch>
Tested-by: Felix Brack <fb@ltec.ch>