soc: qcom: spcom: Add mutex_unlock for device_open err case

This change adds the missing mutex_unlock for device_open of the same
client open twice error case.

Change-Id: Ib75157d0b6d04c6221727778b909f0e3d061b2c8
Signed-off-by: Li Li <liil1@codeaurora.org>
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>