Input: elantech - provide a sysfs knob for crc_enabled

The detection of crc_enabled is known to fail for Fujitsu H730. A DMI
blacklist is added for that, but it can be expected that other laptops will
pop up with this.

Here a sysfs knob is provided to alter the behaviour of crc_enabled.
Writing 0 or 1 to it sets the variable to 0 or 1. Reading it will show the
crc_enabled variable (0 or 1).

Reported-by: Stefan Valouch <stefan@valouch.com>
Signed-off-by: Ulrik De Bie <ulrik.debie-os@e2big.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/elantech.c

@@ -1330,6 +1330,7 @@ ELANTECH_INT_ATTR(reg_25, 0x25);
 ELANTECH_INT_ATTR(reg_26, 0x26);
 ELANTECH_INT_ATTR(debug, 0);
 ELANTECH_INT_ATTR(paritycheck, 0);
+ELANTECH_INT_ATTR(crc_enabled, 0);
 
 static struct attribute *elantech_attrs[] = {
 	&psmouse_attr_reg_07.dattr.attr,
@@ -1344,6 +1345,7 @@ static struct attribute *elantech_attrs[] = {
 	&psmouse_attr_reg_26.dattr.attr,
 	&psmouse_attr_debug.dattr.attr,
 	&psmouse_attr_paritycheck.dattr.attr,
+	&psmouse_attr_crc_enabled.dattr.attr,
 	NULL
 };