tsif: use new clock preparation functions

Replace the clk_enable() with clk_prepare_enable() and replace
clk_disable() with clk_disable_unprepare() functions.
Add a new tasklet so the clocks can be turned off and
unprepared from the irq context in the case of emergency.

Change-Id: Ic63c6c25600069938b414974c5e1237943ffe2e7
Signed-off-by: Joel Nider <jnider@codeaurora.org>