Input: tsc2007 - prevent overflow in pressure calculation

Input: tsc2007 - prevent overflow in pressure calculation

The touch resistance calculation in the tsc2007 driver is prone to
overflow if (z2 - z1) is large and also x is reasonably big. This
overflow results in the driver emitting input events when very little
touch pressure is applied. In these events the x and y coordinates can
be substantially off.

Avoid the overflow by using u64 when calculating resistance value.

Signed-off-by: Johannes Kirchmair <johannes.kirchmair@skidata.com>
Link: https://lore.kernel.org/r/20250129-fix_tsc_calculation_overflow-v2-1-9e51333496ad@skidata.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>