msm: ADSPRPC: Reduce timeout while opening device

When opening new device, wait for pending list to be empty for a
maximum of half second instead of the existing 5secs.

Change-Id: I2d0a96034b71986484da9581331c3989bc619abc
Acked-by: Vishnu Karthik D <vikarthi@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>