serial: a37xx: Do not call get_ref_clk() in _debug_uart_init()

Static inline function _debug_uart_init() should avoid calling external
(non-inline) functions. Therefore do not call get_ref_clk() in
_debug_uart_init() and reimplement its functionality without external
function calls.
Signed-off-by: NPali Rohár <pali@kernel.org>
Reviewed-by: NStefan Roese <sr@denx.de>

drivers/serial/serial_mvebu_a3700.c

@@ -305,6 +305,7 @@ U_BOOT_DRIVER(serial_mvebu) = {
 #ifdef CONFIG_DEBUG_MVEBU_A3700_UART
 
 #include <debug_uart.h>
+#include <mach/soc.h>
 
 static inline void _debug_uart_init(void)
 {
@@ -322,7 +323,8 @@ static inline void _debug_uart_init(void)
 	 * Calculate divider
 	 * baudrate = clock / 16 / divider
 	 */
-	parent_rate = get_ref_clk() * 1000000;
+	parent_rate = (readl(MVEBU_REGISTER(0x13808)) & BIT(9)) ?
+		      40000000 : 25000000;
 	divider = DIV_ROUND_CLOSEST(parent_rate, CONFIG_BAUDRATE * 16);
 	writel(divider, base + UART_BAUD_REG);