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>
diff --git a/board/beacon/imx8mp/spl.c b/board/beacon/imx8mp/spl.c
index 30d577f..6b357d9 100644
--- a/board/beacon/imx8mp/spl.c
+++ b/board/beacon/imx8mp/spl.c
@@ -112,8 +112,6 @@
 
 	arch_cpu_init();
 
-	init_uart_clk(1);
-
 	ret = spl_early_init();
 	if (ret) {
 		debug("spl_init() failed: %d\n", ret);