General serial readers.

Stopped the not needed read request after ok 90 00 answer was received. Upon flush call.
This avoids the long waiting time by some stb's where the sci drivers does not issue an imidiate EINTR or EAGAIN or 0 when there is no card response. Like the vuduo2 sci, it just wait's 4 seconds before it issue 0

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@10040 4b0bc96b-bc66-0410-9d44-ebda105a78c1