exynos/snow: Configure UART peripheral during console initialization.

For Exynos platforms, the UART component on pinmux must be first selected and
configured. This should be done as part of UART console initialization.

Note, that the current implementation hard-codes the device index as UART3,
while the base port can be assigned to different device in Kconfig. This will be
fixed later.

Verified to work on armv7/snow.

Change-Id: Ie63e76e2dac09fec1132573d1b0027fce55333a1
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: http://review.coreboot.org/2315
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-by: David Hendricks <dhendrix@chromium.org>

src/cpu/samsung/exynos5250/uart.c

@@ -119,6 +119,9 @@ static void exynos5_init_dev(void)
 //	struct s5p_uart *const uart = s5p_get_base_uart(dev_index);
 	struct s5p_uart *uart = (struct s5p_uart *)base_port;
 
+	// TODO initialize with correct peripheral id by base_port.
+	exynos_pinmux_config(PERIPH_ID_UART3, PINMUX_FLAG_NONE);
+
 	/* enable FIFOs */
 	writel(0x1, &uart->ufcon);
 	writel(0, &uart->umcon);