Input: libps2 - better handle bad scheduler decisions

Sometimes devices send us their responses in time but due to
unfortunate scheduling decisions the receiving thread does not
get scheduled till much later and we erroneously decide that
device timed out. Work around this problem by checking whether we
received the data we needed instead of checking timeout
condition.

Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>