touchpad: Disable edge palm detection Apple touchpads

This hurts more than it helps, and users complain of dead trackpad edges. Apple touchpads have fairly sophisticated internal palm rejection algorithms going back many years, so let's just disable this one on everything Apple.

Related to: #433 (need to figure out what other hardware may need this, this only fixes it for Apple)

Signed-off-by: Hector Martin marcan@marcan.st