kernel.fitimage.bbclass: remove ramdisk_ctype

set in the ramdisk node the compression property
always to "none", as U-Boot nowadays since commit:

b1307f884a91 ("fit: Support compression for non-kernel components (e.g. FDT)")

decompress non kernel components. Setting compression
to the used comression algorithm now, will end in
fail of your kernel boot with the ramdisk.

This issue is fixed since commit:

bddd98573465 ("fit: Do not automatically decompress ramdisk images")

which now prints a warning in U-Boot, instead of decompressing
the ramdisk, but we should setup compression property correct.

(From OE-Core rev: f963a51544a9a7b1abbaa87c95b3c0279847d697)

Signed-off-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/kernel-fitimage.bbclass

@@ -207,7 +207,6 @@ EOF
 fitimage_emit_section_ramdisk() {
 
 	ramdisk_csum="${FIT_HASH_ALG}"
-	ramdisk_ctype="none"
 	ramdisk_loadline=""
 	ramdisk_entryline=""
 
@@ -218,24 +217,6 @@ fitimage_emit_section_ramdisk() {
 		ramdisk_entryline="entry = <${UBOOT_RD_ENTRYPOINT}>;"
 	fi
 
-	case $3 in
-		*.gz)
-			ramdisk_ctype="gzip"
-			;;
-		*.bz2)
-			ramdisk_ctype="bzip2"
-			;;
-		*.lzma)
-			ramdisk_ctype="lzma"
-			;;
-		*.lzo)
-			ramdisk_ctype="lzo"
-			;;
-		*.lz4)
-			ramdisk_ctype="lz4"
-			;;
-	esac
-
 	cat << EOF >> ${1}
                 ramdisk@${2} {
                         description = "${INITRAMFS_IMAGE}";
@@ -243,7 +224,7 @@ fitimage_emit_section_ramdisk() {
                         type = "ramdisk";
                         arch = "${UBOOT_ARCH}";
                         os = "linux";
-                        compression = "${ramdisk_ctype}";
+                        compression = "none";
                         ${ramdisk_loadline}
                         ${ramdisk_entryline}
                         hash@1 {