Input: elantech - fix detection of touchpads where the revision matches a known rate

Make the check to skip the rate check more lax, so that it applies
to all hw_version 4 models.

This fixes the touchpad not being detected properly on Asus PU551LA
laptops.

Cc: stable@vger.kernel.org
Reported-and-tested-by: David Zafra Gómez <dezeta@klo.es>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: jwrdegoede

drivers/input/mouse/elantech.c

@@ -1376,10 +1376,11 @@ static bool elantech_is_signature_valid(const unsigned char *param)
 		return true;
 
 	/*
-	 * Some models have a revision higher then 20. Meaning param[2] may
-	 * be 10 or 20, skip the rates check for these.
+	 * Some hw_version >= 4 models have a revision higher then 20. Meaning
+	 * that param[2] may be 10 or 20, skip the rates check for these.
 	 */
-	if (param[0] == 0x46 && (param[1] & 0xef) == 0x0f && param[2] < 40)
+	if ((param[0] & 0x0f) >= 0x06 && (param[1] & 0xaf) == 0x0f &&
+	    param[2] < 40)
 		return true;
 
 	for (i = 0; i < ARRAY_SIZE(rates); i++)