Input: spear_keyboard - reconfigure operating frequency on suspend

On some platform it may happen that the input clock to keyboard may
change during suspend, thus impacting its wakeup capability.

There is no means for keyboard driver to know this frequency before
hand. Hence introduce a platform data 'suspended_rate' which indicates
the frequency during suspend at which keyboard operates.

Accordingly reprogram keyboard while going into suspend and restore
original configuration at the time of resume.

Signed-off-by: Shiraz Hashim <shiraz.hashim@st.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>