board: atmel: remove calls to debug_uart_init

Since 0dba4586 ("arm: Init the debug UART") ,
the debug_uart_init is now called from crt.S

It's no longer required to call it from the board file.

With the current code, the banned <debug_uart> is printed twice:

<debug_uart>

<debug_uart>

U-Boot 2022.07-rc4-00089-gee3d158fa8 (Jun 08 2022 - 17:39:29 +0300)

Remove all calls from board_early_init_f .

Suggested-by: Balamanikandan Gunasundar <Balamanikandan.Gunasundar@microchip.com>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>