usb: rockchip: implement skeleton for K_FW_GET_CHIP_VER command

Chip Version is a string saved in BOOTROM address space Little Endian.

Ex for rk3288: 0x33323041 0x32303134 0x30383133 0x56323030
which brings:  320A20140813V200

Note that memory version do invert MSB/LSB so printing the char
buffer would show: A02341023180002V

Signed-off-by: Alberto Panizzo <alberto@amarulasolutions.com>
diff --git a/doc/README.rockusb b/doc/README.rockusb
index 5405dc4..3a93edc 100644
--- a/doc/README.rockusb
+++ b/doc/README.rockusb
@@ -42,9 +42,12 @@
 
 sudo rkdeveloptool wl  64 <U-Boot binary>
 
-There are plenty of Rockusb command. but wl(write lba) and
-rd(reboot) command. These two command can let people flash
-image to device.
+Current set of rkdeveloptool commands supported:
+- rci: Read Chip Info
+- rfi: Read Flash Id
+- rd : Reset Device
+- td : Test Device Ready
+- wl : Write blocks using LBA
 
 To do
 -----