tspp: Fix incorrect usage of clk_disable to support PM

The TSPP driver uses clk_prepare_enable() API to use the appropriate
clocks. When the device is not used, clk_disable_unprepare() should
be called. However, clk_disable() was used by mistake instead.

Change-Id: I70f8e9e8a7d2aef3a781be160b72096252e964de
Signed-off-by: Liron Kuch <lkuch@codeaurora.org>