Input: synaptics-rmi4 - disable the relative position IRQ in the F12 driver

This patch fixes an issue seen on HID touchpads which report finger
positions using RMI4 Function 12. The issue manifests itself as
spurious button presses as described in:
https://www.spinics.net/lists/linux-input/msg58618.html

Commit 24d28e4f

 ("Input: synaptics-rmi4 - convert irq distribution
to irq_domain") switched the RMI4 driver to using an irq_domain to handle
RMI4 function interrupts. Functions with more then one interrupt now have
each interrupt mapped to their own IRQ and IRQ handler. The result of
this change is that the F12 IRQ handler was now getting called twice. Once
for the absolute data interrupt and once for the relative data interrupt.
For HID devices, calling rmi_f12_attention() a second time causes the
attn_data data pointer and size to be set incorrectly. When the touchpad
button is pressed, F30 will generate an interrupt and attempt to read the
F30 data from the invalid attn_data data pointer and report incorrect
button events.

This patch disables the F12 relative interrupt which prevents
rmi_f12_attention() from being called twice.

Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Reported-by: Simon Wood <simon@mungewell.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191025002527.3189-2-aduggan@synaptics.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>