adb: temporary fix to limit USB transfers to 4KB.

Dragonboards currently can't handle large USB transfers, this lowers
the max transfer size to get the board working for now.

Longer-term we'll either get the Dragonboard working or land something
upstream that will allow each board to custom-define this value.

Bug: http://b/24905170.
Change-Id: If87c4dd3ed4522c3e15b8a50920049fdbe9a82ea
(cherry picked from commit 58e6732cb0dad86946e98fdab79cff43be6a03ce)

adb/adb.h

diff --git a/adb/adb.h b/adb/adb.h
index c284c8c..c4fbe50 100644
--- a/adb/adb.h
+++ b/adb/adb.h
@@ -30,7 +30,8 @@
 
 constexpr size_t MAX_PAYLOAD_V1 = 4 * 1024;
 constexpr size_t MAX_PAYLOAD_V2 = 256 * 1024;
-constexpr size_t MAX_PAYLOAD = MAX_PAYLOAD_V2;
+// Temporary revert back to V1 for Dragonboard (http://b/24905170).
+constexpr size_t MAX_PAYLOAD = MAX_PAYLOAD_V1;
 
 #define A_SYNC 0x434e5953
 #define A_CNXN 0x4e584e43