HID: wacom: Fix logic used for 3rd barrel switch emulation

When support was added for devices using an explicit 3rd barrel switch,
the logic used by devices emulating this feature was broken. The 'if'
statement / block that was introduced only handles the case where the
button is pressed (i.e. 'barrelswitch' and 'barrelswitch2' are both set)
but not the case where it is released (i.e. one or both being cleared).
This results in a BTN_STYLUS3 "down" event being sent when the button
is pressed, but no "up" event ever being sent afterwards.

This patch restores the previously-used logic for determining button
states in the emulated case so that switches are reported correctly
again.

Link: https://github.com/linuxwacom/xf86-input-wacom/issues/292


Fixes: 6d09085b ("HID: wacom: Adding Support for new usages")
CC: stable@vger.kernel.org #v5.19+
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Tested-by: Joshua Dickens <joshua.dickens@wacom.com>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>