Input: spear-keyboard - configure device according to supplied mode

Let platform pass mode information to keyboard driver according to which
it configures itself. The mode can be
 - KEYPAD_9x9     0
 - KEYPAD_6x6     1
 - KEYPAD_2x2     2

Signed-off-by: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>