pixma: updated status for MG5400 Series

See http://lists.alioth.debian.org/pipermail/sane-devel/2017-March/035072.html
and http://lists.alioth.debian.org/pipermail/sane-devel/2017-March/035082.html

doc/descriptions/pixma.desc

@@ -163,8 +163,8 @@
 :model "PIXMA MG5400 Series"
 :interface "USB"
 :usbid "0x04a9" "0x1764"
-:status :untested
-:comment "Testers needed!"
+:status :good
+:comment "All resolutions supported (up to 2400DPI)."
 
 :model "PIXMA MG5500 Series"
 :interface "USB WiFi"