global: Migrate CONFIG_I2C_MULTI_BUS to CFG

Perform a simple rename of CONFIG_I2C_MULTI_BUS to CFG_I2C_MULTI_BUS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/i2c.h b/include/i2c.h
index 51390f8..3811b26 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -930,7 +930,7 @@
  * only for backwardcompatibility, should go away if we switched
  * completely to new multibus support.
  */
-#if CONFIG_IS_ENABLED(SYS_I2C_LEGACY) || defined(CONFIG_I2C_MULTI_BUS)
+#if CONFIG_IS_ENABLED(SYS_I2C_LEGACY) || defined(CFG_I2C_MULTI_BUS)
 # if !defined(CFG_SYS_MAX_I2C_BUS)
 #  define CFG_SYS_MAX_I2C_BUS		2
 # endif