Revert "fastboot: add preflash command to help with large downloads+flash"

This reverts commit 6f1cd0b2ad7a16d4ec0b5324f992cae33dc34f34.

It causes some devices to fail (b/9581613). Revert for now.

Change-Id: I076158c704c2b4f0459322aa157c19ebd0c4615f
diff --git a/fastboot/fastboot_protocol.txt b/fastboot/fastboot_protocol.txt
index eede5d1..2248992 100644
--- a/fastboot/fastboot_protocol.txt
+++ b/fastboot/fastboot_protocol.txt
@@ -1,5 +1,5 @@
 
-FastBoot  Version  0.4++
+FastBoot  Version  0.4
 ----------------------
 
 The fastboot protocol is a mechanism for communicating with bootloaders
@@ -67,6 +67,10 @@
 Example Session
 ---------------
 
+Host:    "getvar:version"        request version variable
+
+Client:  "OKAY0.4"               return version "0.4"
+
 Host:    "getvar:nonexistant"    request some undefined variable
 
 Client:  "OKAY"                  return value ""
@@ -119,11 +123,6 @@
   "flash:%s"           Write the previously downloaded image to the
                        named partition (if possible).
 
-  "preflash:%s"        Optionally prepare for a download + flash.
-                       E.g. flash directly during download. To deal with a
-                       failed "flash" followed by a "boot", we send
-                       "preflash:".
-
   "erase:%s"           Erase the indicated partition (clear to 0xFFs)
 
   "boot"               The previously downloaded data is a boot.img
@@ -141,9 +140,7 @@
 
   "powerdown"          Power off the device.
 
-* Note about sparse files
-  Large files can be split up using libsparse, and sent to the bootloader
-  as repeated chunks of "download:%08x" + "flash:%s".
+
 
 Client Variables
 ----------------
@@ -154,6 +151,9 @@
 
 The various currently defined names are:
 
+  version             Version of FastBoot protocol supported.
+                      It should be "0.3" for this document.
+
   version-bootloader  Version string for the Bootloader.
 
   version-baseband    Version string of the Baseband Software