kbuild: fix 'make rpm' when CONFIG_LOCALVERSION_AUTO=y and using SCM tree

Running 'make rpm' fails when CONFIG_LOCALVERSION_AUTO=y and using a kernel source
tree under SCM.  This is due to KERNELRELEASE being different when the initial make
is run and when make is run from rpmbuild.

mkspec creates kernel.spec using KERNELRELEASE:

<mkspec>
echo "%files"
echo '%defattr (-, root, root)'
echo "%dir /lib/modules"
echo "/lib/modules/$KERNELRELEASE"
echo "/lib/firmware"
echo "/boot/*"
echo ""
</mkspec>

When CONFIG_LOCALVERSION_AUTO=y scripts/setlocalversion is called and grabs any
additional version info from SCM.  Next, the srctree is tarred up and SCM
information is excluded.

rpmbuild reruns make and in the process generates a new include/config/kernel.release
and thus a new KERNELRELEASE.  However this time the SCM information is gone so
KERNELRELEASE no longer has the additional version information.  When "make modules_install"
runs, it uses the new KERNELRELEASE value to determine where to install the m...