board: gateworks: gw_ventana: convert to DM_I2C

convert to DM_I2C for U-Boot while leaving SPL legacy I2C:
 - Move I2C config from common to SPL
 - Move PMIC config from common to SPL (no need to re-configure pmic)
 - add DM_I2C support to eeprom/gsc functions shared by SPL and U-Boot

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/configs/gwventana_gw5904_defconfig b/configs/gwventana_gw5904_defconfig
index 8a50506..1d95fb0 100644
--- a/configs/gwventana_gw5904_defconfig
+++ b/configs/gwventana_gw5904_defconfig
@@ -90,7 +90,7 @@
 CONFIG_DM=y
 CONFIG_BOUNCE_BUFFER=y
 CONFIG_DWC_AHSATA=y
-CONFIG_SYS_I2C_LEGACY=y
+CONFIG_DM_I2C=y
 CONFIG_SPL_SYS_I2C_LEGACY=y
 CONFIG_SYS_I2C_MXC=y
 CONFIG_LED=y