platform/x86: dell-wmi: add new backlight events

Add events with a type of 0x0010 and a code of 0x57 / 0x58,
this silences the following messages being logged on a
Dell Inspiron 5593:

dell_wmi: Unknown key with type 0x0010 and code 0x0057 pressed
dell_wmi: Unknown key with type 0x0010 and code 0x0058 pressed

These are brightness events and will be handled by acpi-video
Signed-off-by: Y Paritcher <y.linux@paritcher.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/dell-wmi.c

@@ -255,6 +255,10 @@ static const struct key_entry dell_wmi_keymap_type_0010[] = {
 	/* Keyboard backlight change notification */
 	{ KE_IGNORE, 0x3f, { KEY_RESERVED } },
 
+	/* Backlight brightness level */
+	{ KE_KEY,    0x57, { KEY_BRIGHTNESSDOWN } },
+	{ KE_KEY,    0x58, { KEY_BRIGHTNESSUP } },
+
 	/* Mic mute */
 	{ KE_KEY, 0x150, { KEY_MICMUTE } },