[media] c8sectpfe: Remove clk_disable_unprepare hacks

Now that CLK_PROC_STFE is defined as a critical clock in
DT, we can remove the commented clk_disable_unprepare from
the c8sectpfe driver. This means we now have balanced
clk*enable/disable calls in the driver, but on STiH407
family the clock in reality will never actually be disabled.

This is due to a HW bug where once the IP has been configured
and the SLIM core is running, disabling the clock causes a
unrecoverable bus lockup.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>