Convert CONFIG_SYS_I2C_DAVINCI to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_I2C_DAVINCI

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/da850_am18xxevm_defconfig b/configs/da850_am18xxevm_defconfig
index 779d9cf..c61d78e 100644
--- a/configs/da850_am18xxevm_defconfig
+++ b/configs/da850_am18xxevm_defconfig
@@ -40,6 +40,7 @@
 CONFIG_DA8XX_GPIO=y
 CONFIG_DM_I2C=y
 CONFIG_DM_I2C_COMPAT=y
+CONFIG_SYS_I2C_DAVINCI=y
 CONFIG_MTD_DEVICE=y
 CONFIG_MTD_PARTITIONS=y
 CONFIG_DM_SPI_FLASH=y