msm: tsc: Fix deadlock when tsc_mux receive NULL parameter

Add release of a taken mutex that was missing in the
tsc_mux device in case of invalid parameters.

Change-Id: I3f647d3118295e10b436355ba8fe2fa2a4e6b4fd
Signed-off-by: Anat Etzion-Fuchs <aetzion@codeaurora.org>