payloads/external: Add support for coreDOOM payload

coreDOOM is a port of DOOM to libpayload, based on the doomgeneric
source port. It renders the game to the coreboot linear framebuffer,
and loads WAD files from CBFS.

Tested with QEMU i440fx/q35 and a Dell Latitude E6400 using the
libgfxinit provided linear framebuffer.

Project page: https://github.com/nic3-14159/coreDOOM

Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>
Change-Id: Ice0403b003a4b2717afee585f28303c2f5abea5d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57222
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>

payloads/external/coreDOOM/Kconfig.secondary

@@ -0,0 +1,25 @@
+if COREDOOM_SECONDARY_PAYLOAD
+
+config COREDOOM_WAD_FILE
+	string "DOOM WAD file"
+	depends on COREDOOM_SECONDARY_PAYLOAD
+	default "doom.wad"
+	help
+	  Add a WAD file to be loaded by coreDOOM.
+
+	  A WAD file contains all the game data for the Doom-engine, and
+	  is required to play the game.
+
+	  A list of the WAD files included in the official games can be
+	  found here: https://doomwiki.org/wiki/IWAD
+	  These WADs can be extracted from copies of the game that you
+	  own, and the shareware WADs may be freely downloaded from the
+	  internet.
+
+	  For a completely free (as in freedom) experience, the Freedoom
+	  project (https://freedoom.github.io) provides original game
+	  content under the BSD license. Other WADs not mentioned here are
+	  also available and may be found from various sources such as
+	  the internet and copies of other games using the Doom engine.
+
+endif