Input: elantech - add resolution query support for v4 hardware

It turns out that v4's firmware provides a command so we can query
the resolution. Let's use it.

Signed-off-by: JJ Ding <jj_ding@emc.com.tw>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/mouse/elantech.h b/drivers/input/mouse/elantech.h
index 08d00bd..46db3be 100644
--- a/drivers/input/mouse/elantech.h
+++ b/drivers/input/mouse/elantech.h
@@ -20,6 +20,7 @@
 #define ETP_FW_VERSION_QUERY		0x01
 #define ETP_CAPABILITIES_QUERY		0x02
 #define ETP_SAMPLE_QUERY		0x03
+#define ETP_RESOLUTION_QUERY		0x04
 
 /*
  * Command values for register reading or writing