mfd: ti_am335x_tscadc: Fix TSC resume

mfd: ti_am335x_tscadc: Fix TSC resume

In the resume path, the ADC invokes am335x_tsc_se_set_cache() with 0 as
the steps argument if continous mode is not in use. This in turn disables
all steps and so the TSC is not working until one ADC sampling is
performed.

This patch fixes it by writing the current cached mask instead of the
passed steps.

Fixes: 7ca6740cd1cd ("mfd: input: iio: ti_amm335x: Rework TSC/ADCA
synchronization")
Cc: stable@vger.kernel.org # v3.13+
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>