usb: rockchip: implement K_FW_LBA_READ_10 command

This patch implement reading blocks form selected device with
LBA addressing.

Corresponding command on workstation is:
rkdeveloptool rl <start_blk> <blk_cnt> <file>

While we support reading more than one blocks per K_FW_LBA_READ_10
request, rkdeveloptool and original rockchip tool do perform
chunk reads limiting the maximum size per chunk far lower
than max int values.

Signed-off-by: Alberto Panizzo <alberto@amarulasolutions.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/README.rockusb b/doc/README.rockusb
index 3a93edc..7f58296 100644
--- a/doc/README.rockusb
+++ b/doc/README.rockusb
@@ -47,6 +47,7 @@
 - rfi: Read Flash Id
 - rd : Reset Device
 - td : Test Device Ready
+- rl : Read blocks using LBA
 - wl : Write blocks using LBA
 
 To do