hwdb: fix warning "atkbd serio0: Unknown key pressed" (#5772)

At each time pressing the WiFi Fn key on Dell Latitude E7270 laptop, the system
reports the following error/warning messages:

  atkbd serio0: Unknown key pressed (translated set 2, code 0x88 on isa0060/serio0).
  atkbd serio0: Use 'setkeycodes e008 ' to make it known.

This is due to commit 0e33634 which was added to fix
https://bugs.launchpad.net/ubuntu/+source/udev/+bug/1441849.

However on Dell Latitude E7* models, we need to restore the old generic
behavior which consists in ignoring the key event since it's already done by
the HW.

Indeed the hardware has a specific driver (dell_wmi) to handle rfkill in the
hardware level. So, as long as the hardware handles, the best is to leave as
is.

This patch was originally written by Takashi Iwai.

Fixes #5047

hwdb/60-keyboard.hwdb

@@ -314,6 +314,10 @@ evdev:atkbd:dmi:bvn*:bvr*:bd*:svnDell*:pnPrecision*:pvr*
  KEYBOARD_KEY_88=!                                      # wireless switch
  KEYBOARD_KEY_9e=!f21
 
+# Dell Latitude E7*
+evdev:atkbd:dmi:bvn*:bvr*:bd*:svnDell*:pnLatitude*E7*:pvr*
+ KEYBOARD_KEY_88=unknown                                # Fn-PrtScr rfkill - handled in HW
+
 # Dell XPS
 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnDell*:pnXPS*:pvr*
  KEYBOARD_KEY_8c=!unknown