image_types_phosphor: drop overlay

The overlay image type doesn't have any code behind it and thus
selecting it in IMAGE_FSTYPES would result in unexpected behavior.

An overlay image type still exists but it was renamed to mtd-static
in an earlier refactor, and this cleanup was omitted.

Tested: Built witherspoon and palmetto images
Change-Id: I7eb41afcf25ae2d251bf671dd0e5a18e1064f7c4
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/classes/image_types_phosphor.bbclass b/classes/image_types_phosphor.bbclass
index 8c1599c..de1883f 100644
--- a/classes/image_types_phosphor.bbclass
+++ b/classes/image_types_phosphor.bbclass
@@ -17,15 +17,14 @@
 FLASH_UBI_BASETYPE ?= "${IMAGE_BASETYPE}"
 FLASH_UBI_OVERLAY_BASETYPE ?= "ubifs"
 
-IMAGE_TYPES += "overlay mtd-static mtd-static-alltar mtd-static-tar mtd-ubi mtd-ubi-tar"
+IMAGE_TYPES += "mtd-static mtd-static-alltar mtd-static-tar mtd-ubi mtd-ubi-tar"
 
-IMAGE_TYPEDEP_overlay = "${IMAGE_BASETYPE}"
 IMAGE_TYPEDEP_mtd-static = "${IMAGE_BASETYPE}"
 IMAGE_TYPEDEP_mtd-static-tar = "${IMAGE_BASETYPE}"
 IMAGE_TYPEDEP_mtd-static-alltar = "mtd-static"
 IMAGE_TYPEDEP_mtd-ubi = "${FLASH_UBI_BASETYPE}"
 IMAGE_TYPEDEP_mtd-ubi-tar = "${FLASH_UBI_BASETYPE}"
-IMAGE_TYPES_MASKED += "overlay mtd-static mtd-static-alltar mtd-static-tar mtd-ubi mtd-ubi-tar"
+IMAGE_TYPES_MASKED += "mtd-static mtd-static-alltar mtd-static-tar mtd-ubi mtd-ubi-tar"
 
 # Flash characteristics in KB unless otherwise noted
 FLASH_SIZE ?= "32768"