i2c: Rename CONFIG_SYS_I2C to CONFIG_SYS_I2C_LEGACY

It is quite confusing that CONFIG_SYS_I2C selects the legacy I2C and
CONFIG_DM_I2C selects the current I2C. The deadline to migrate I2C is less
than a year away.

Also we want to have a CONFIG_I2C for U-Boot proper just like we have
CONFIG_SPL_I2C for SPL, so we can simplify the Makefile rules.

Rename this symbol so it is clear it is going away.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher <hs@denx.de>
diff --git a/board/compulab/common/Makefile b/board/compulab/common/Makefile
index 7ba92f5..842fb3b 100644
--- a/board/compulab/common/Makefile
+++ b/board/compulab/common/Makefile
@@ -5,6 +5,6 @@
 # Author: Igor Grinberg <grinberg@compulab.co.il>
 
 obj-y				+= common.o
-obj-$(CONFIG_SYS_I2C)		+= eeprom.o
+obj-$(CONFIG_SYS_I2C_LEGACY)		+= eeprom.o
 obj-$(CONFIG_LCD)		+= omap3_display.o
 obj-$(CONFIG_SMC911X)		+= omap3_smc911x.o