kbuild: verify that $DEPMOD is installed

Verify that 'depmod' ($DEPMOD) is installed.
This is a partial revert of commit 620c231c7a
("kbuild: do not check for ancient modutils tools").

Also update Documentation/process/changes.rst to refer to
kmod instead of module-init-tools.

Fixes kernel bugzilla #198965:
https://bugzilla.kernel.org/show_bug.cgi?id=198965

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Chih-Wei Huang <cwhuang@linux.org.tw>
Cc: stable@vger.kernel.org # any kernel since 2012
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/depmod.sh

@@ -10,10 +10,16 @@ fi
 DEPMOD=$1
 KERNELRELEASE=$2
 
-if ! test -r System.map -a -x "$DEPMOD"; then
+if ! test -r System.map ; then
 	exit 0
 fi
 
+if [ -z $(command -v $DEPMOD) ]; then
+	echo "'make modules_install' requires $DEPMOD. Please install it." >&2
+	echo "This is probably in the kmod package." >&2
+	exit 1
+fi
+
 # older versions of depmod require the version string to start with three
 # numbers, so we cheat with a symlink here
 depmod_hack_needed=true