Input: alps - process_bitmap: fix counting of high point bits

alps_process_bitmap was resetting the point bit-count as soon as it saw
2 0 bits in a row. This means that unless the high point actually is at
the end of the bitmap, it would always get its num_bits set to 0.

Instead reset num_bits to 0 on a 0->1 transition, so that with > 2 fingers
we only count the number of bits occupied by the highest finger.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>