powerpc/boot: Add version to install filenames

Rather than replacing the versionless vmlinux and System.map files,
copy to files with the version info appended.

Additionally, since executing the script is a last resort option,
inform the user about the missing `installkernel` command and the
location of the installation.

This work is adapted from `arch/s390/boot/install.sh`, and also matches
the behaviour of arm, arm64 and riscv.

Signed-off-by: Nick Child <nnac123@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230314164442.124929-1-nnac123@linux.ibm.com

Author: Nick Child

arch/powerpc/boot/install.sh

@@ -21,13 +21,17 @@ set -e
 # this should work for both the pSeries zImage and the iSeries vmlinux.sm
 image_name=`basename $2`
 
-if [ -f $4/$image_name ]; then
-	mv $4/$image_name $4/$image_name.old
+
+echo "Warning: '${INSTALLKERNEL}' command not available... Copying" \
+     "directly to $4/$image_name-$1" >&2
+
+if [ -f $4/$image_name-$1 ]; then
+	mv $4/$image_name-$1 $4/$image_name-$1.old
 fi
 
-if [ -f $4/System.map ]; then
-	mv $4/System.map $4/System.old
+if [ -f $4/System.map-$1 ]; then
+	mv $4/System.map-$1 $4/System-$1.old
 fi
 
-cat $2 > $4/$image_name
-cp $3 $4/System.map
+cat $2 > $4/$image_name-$1
+cp $3 $4/System.map-$1