arm: mvebu: a3720: Create Kconfig option for I2C_MV

Move the config option CONFIG_I2C_MV to a Kconfig option
CONFIG_SYS_I2C_MV and move the default definition from config header
files into defconfigs.

Signed-off-by: Marek BehĂșn <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/configs/uDPU_defconfig b/configs/uDPU_defconfig
index 17278ae..fa2293b 100644
--- a/configs/uDPU_defconfig
+++ b/configs/uDPU_defconfig
@@ -54,6 +54,7 @@
 CONFIG_CLK_MVEBU=y
 CONFIG_DM_I2C=y
 CONFIG_DM_I2C_GPIO=y
+CONFIG_SYS_I2C_MV=y
 CONFIG_MISC=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_SDMA=y