imx: Use MXC_I2C_CLK in imx i2c driver

i2c didn't work on imx25 due to missing MXC_IPG_PERCLK. Now using
MXC_I2C_CLK on all imx systems using i2c.

Signed-off-by: Matthias Weisser <weisserm@arcor.de>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/include/asm/arch-mx5/clock.h b/arch/arm/include/asm/arch-mx5/clock.h
index 8d8fa18..21febd8 100644
--- a/arch/arm/include/asm/arch-mx5/clock.h
+++ b/arch/arm/include/asm/arch-mx5/clock.h
@@ -36,6 +36,7 @@
 	MXC_DDR_CLK,
 	MXC_NFC_CLK,
 	MXC_PERIPH_CLK,
+	MXC_I2C_CLK,
 };
 
 u32 imx_get_uartclk(void);