cmd_eeprom: make it possible to define the used i2c bus

A SoC like the i.MX6 supports more then one i2c bus. In oder to be
able to use the eeprom command add a new define to specify the
i2c bus to use. If CONFIG_SYS_I2C_EEPROM_BUS is not defined there
is no functional change, else a call to i2c_set_bus_num(..) is
done before calling i2c_read(..) and i2c_write(..).

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Acked-by: Stefano Babic <sbabic@denx.de>

README

@@ -4341,6 +4341,9 @@ to save the current settings.
 	  If defined, specified the chip address of the EEPROM device.
 	  The default address is zero.
 
+	- CONFIG_SYS_I2C_EEPROM_BUS:
+	  If defined, specified the i2c bus of the EEPROM device.
+
 	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
 	  If defined, the number of bits used to address bytes in a
 	  single page in the EEPROM device.  A 64 byte page, for example

common/cmd_eeprom.c

@@ -161,6 +161,9 @@ int eeprom_read (unsigned dev_addr, unsigned offset, uchar *buffer, unsigned cnt
 #if defined(CONFIG_SPI) && !defined(CONFIG_ENV_EEPROM_IS_ON_I2C)
 		spi_read (addr, alen, buffer, len);
 #else
+#if defined(CONFIG_SYS_I2C_EEPROM_BUS)
+		i2c_set_bus_num(CONFIG_SYS_I2C_EEPROM_BUS);
+#endif
 		if (i2c_read(addr[0], offset, alen - 1, buffer, len))
 			rcode = 1;
 #endif
@@ -338,6 +341,9 @@ int eeprom_write (unsigned dev_addr, unsigned offset, uchar *buffer, unsigned cn
 		}
 		/* Write is enabled ... now write eeprom value.
 		 */
+#endif
+#if defined(CONFIG_SYS_I2C_EEPROM_BUS)
+		i2c_set_bus_num(CONFIG_SYS_I2C_EEPROM_BUS);
 #endif
 		if (i2c_write(addr[0], offset, alen - 1, buffer, len))
 			rcode = 1;