configs: am65x_evm_r5: Activate early console functionality

Activate early console functionality on AM654x devices to allow for an
alternate serial port to be used to support UART-based boot. This is so
that System Firmware (SYSFW) can get loaded over the serial port prior
to the main console being brought up and made available.

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>