mv_i2c: use structure to replace the direclty define

Add i2c_clk_enable in the cpu specific code, since previous platform it,
while new platform don't need. In the pantheon and armada100 platform,
this function is defined as NULL one.

Acked-by: Heiko Schocher <hs@denx.de>
Acked-by: Prafulla Wadaskar <prafulla@marvell.com>
Signed-off-by: Lei Wen <leiwen@marvell.com>
diff --git a/arch/arm/cpu/pxa/cpu.c b/arch/arm/cpu/pxa/cpu.c
index 7d49cbb..9970a4b 100644
--- a/arch/arm/cpu/pxa/cpu.c
+++ b/arch/arm/cpu/pxa/cpu.c
@@ -318,3 +318,13 @@
 	pxa_clock_setup();
 	return 0;
 }
+
+void i2c_clk_enable(void)
+{
+	/* set the global I2C clock on */
+#ifdef CONFIG_CPU_MONAHANS
+	writel(readl(CKENB) | (CKENB_4_I2C), CKENB);
+#else
+	writel(readl(CKEN) | CKEN14_I2C, CKEN);
+#endif
+}