board: beacon: imx8mp: Let clock system enable UART clock

Now that the UART driver can enable the required clocks, remove
the hard-coded clock enable.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>

board/beacon/imx8mp/spl.c

@@ -112,8 +112,6 @@ void board_init_f(ulong dummy)
 
 	arch_cpu_init();
 
-	init_uart_clk(1);
-
 	ret = spl_early_init();
 	if (ret) {
 		debug("spl_init() failed: %d\n", ret);