Input: atmel_mxt_ts - fix multiple <linux/property.h> includes

Both v4.16-rc7 commit 93afb1d6 ("Input: atmel_mxt_ts - switch from
OF to generic device properties") and v4.16-rc7 commit 96a938aa
("Input: atmel_mxt_ts - remove platform data support") added includes of
"<linux/property.h>".  Remove one of the duplicate includes to fix this.

Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>