Input: edt-ft5x06 - fix an i2c write for M09 support

The driver sends 3 bytes instead of 2 when accessing a register on the M09
firmware, so writing to gain seems to overflow into the offset register.

Signed-off-by: Robert Woerle <robert@linuxdevelopment.de>
Acked-By: Simon Budig <simon.budig@kernelconcepts.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>