cbfs/payload type: Fix build warning and whitespace in name

Currently, adding a payload to CBFS using the build system, the warning
below is shown.

    W: Unknown type 'payload' ignored

Update payload type from "simple elf" to "simple_elf" and rename the
word "payload" to "simple_elf" in all Makefiles.

Fixes: 4f5bed52 (cbfs: Rename CBFS_TYPE_PAYLOAD to CBFS_TYPE_SELF)
Change-Id: Iccf6cc889b7ddd0c6ae04bda194fe5f9c00e495d
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/26240
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

payloads/external/Makefile.inc

@@ -48,7 +48,7 @@ $(CONFIG_CBFS_PREFIX)/payload-file := $(CONFIG_PAYLOAD_FILE)
 ifeq ($(CONFIG_PAYLOAD_IS_FLAT_BINARY),y)
 $(CONFIG_CBFS_PREFIX)/payload-type := flat-binary
 else
-$(CONFIG_CBFS_PREFIX)/payload-type := payload
+$(CONFIG_CBFS_PREFIX)/payload-type := simple_elf
 endif
 $(CONFIG_CBFS_PREFIX)/payload-compression := $(CBFS_PAYLOAD_COMPRESS_FLAG)
 $(CONFIG_CBFS_PREFIX)/payload-options := $(ADDITIONAL_PAYLOAD_CONFIG)
@@ -184,14 +184,14 @@ payloads/external/tint/tint/tint.elf tint:
 
 cbfs-files-$(CONFIG_TINT_SECONDARY_PAYLOAD) += img/tint
 img/tint-file := payloads/external/tint/tint/tint.elf
-img/tint-type := payload
+img/tint-type := simple_elf
 img/tint-compression := $(CBFS_SECONDARY_PAYLOAD_COMPRESS_FLAG)
 
 # Memtest86+
 
 cbfs-files-$(CONFIG_MEMTEST_SECONDARY_PAYLOAD) += img/memtest
 img/memtest-file := payloads/external/Memtest86Plus/memtest86plus/memtest
-img/memtest-type := payload
+img/memtest-type := simple_elf
 img/memtest-compression := $(CBFS_SECONDARY_PAYLOAD_COMPRESS_FLAG)
 
 ifeq ($(CONFIG_CONSOLE_SERIAL)$(CONFIG_DRIVERS_UART_8250IO),yy)