msm: cvp: remove additional checks in response_handler

possibility of OOB access on device->response_pkt in
__response_handler. for e.x if msg queue contains 1000
messages and all 1000 were read and queue is empty.
So __get_q_size api will return zero and _iface_msgq_read
will go in an infinite loop, even if packet_count
== max_packets.

Change-Id: I417bfe3b85c1d2fa6a3c7ae1f96d3b081b13670d
Acked-by: Sumit LNU <suchawla@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>