GDB RSP behaviour

[mingxguo27]

There are currently two issues with the remote connection:

1. The connection is slower than expected. Sometimes a command requires a few resends (currently each receive has one second of timeout window) to get acknowledged.
2. Command "g" (read general registers) gets unexpected respond. It should receive 17 (number of registers) * 4 (register length) hex bytes but sometimes gets longer response (with correct checksum).