soc/marvell/armada38x: Add i2c driver for armada38x

Port i2c driver from uboot to coreboot

BUG=chrome-os-partner:47462
TEST=emerge-cyclone coreboot
BRANCH=tot

Change-Id: I8ce2a965acaed68ad0f0518648490ec471c6810b
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 4c2e9592662787ebed1d0aa8cafaa00fd12c2e9c
Original-Change-Id: If791228edf29405fa4b2f959a21510bd7da9865b
Original-Signed-off-by: Ruilin Hao <rlhao@marvell.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/313342
Original-Commit-Ready: Kan Yan <kyan@google.com>
Original-Tested-by: Kan Yan <kyan@google.com>
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/13113
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/soc/marvell/armada38x/uart.c

@@ -21,6 +21,7 @@
 #include <stdint.h>
 #include <assert.h>
 #include <soc/common.h>
+#include <soc/clock.h>
 
 struct armada38x_uart {
 	union {
@@ -94,7 +95,7 @@ static int armada38x_uart_tst_byte(struct armada38x_uart *uart_ptr)
 
 unsigned int uart_platform_refclk(void)
 {
-	return MV_BOARD_TCLK_250MHZ;
+	return mv_tclk_get();
 }
 
 uintptr_t uart_platform_base(int idx)