Add support for Maxim's DS4510 I2C device

Initial support for the DS4510, a CPU supervisor with
integrated EEPROM, SRAM, and 4 programmable non-volatile
GPIO pins. The CONFIG_DS4510 define enables support
for the device while the CONFIG_CMD_DS4510 define
enables the ds4510 command. The additional
CONFIG_DS4510_INFO, CONFIG_DS4510_MEM, and
CONFIG_DS4510_RST defines add additional sub-commands
to the ds4510 command when defined.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/README b/README
index 132650e..ad792d3 100644
--- a/README
+++ b/README
@@ -592,6 +592,10 @@
 		CONFIG_CMD_DHCP		* DHCP support
 		CONFIG_CMD_DIAG		* Diagnostics
 		CONFIG_CMD_DOC		* Disk-On-Chip Support
+		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
+		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
+		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
+		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
 		CONFIG_CMD_DTT		* Digital Therm and Thermostat
 		CONFIG_CMD_ECHO		  echo arguments
 		CONFIG_CMD_EEPROM	* EEPROM read/write support