Input: elan_i2c - fix calculating number of x and y traces.

According to Elan's firmware engineers we should not be subtracting 1 form
the raw number of x and y traces so that the pitch size is correct. For
example, if the touchpad x resolution is 2800 and x trace number is 20,
the pitch size of x should be 2800/20 = 140, not 2800/19 = 147.36.

Signed-off-by: Duson Lin <dusonlin@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>