Fix non-aio USB read issue for fastbootd

non-aio USB read function was stuck in a loop waiting for more data
because data length parameter is always set 64 for fastbootd commands.
It should be a normal case to get less data than expected
since lengths of these commands are usually less than 64.
Add logic to check this and one more parameter to distinguish
fastbootd from general adbd case.

Bug: 133189029
Test: try various fastbootd commands
Change-Id: I6690324840d78f3f1e04235040301520329976db
Merged-In: I6690324840d78f3f1e04235040301520329976db