kbuild: rpm-pkg: remove unneeded KERNELRELEASE from modules/headers_install

This is a temporary workaround added by commit f6e09b07 ("kbuild:
do not put .scmversion into the source tarball").

Since commit 1cb86b6c ("kbuild: save overridden KERNELRELEASE in
include/config/kernel.release"), the user-supplied KERNELRELEASE is
saved in include/config/kernel.release.

Remove it again.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>

scripts/package/mkspec

@@ -99,8 +99,8 @@ $S
 	%else
 	cp \$($MAKE -s image_name) %{buildroot}/boot/vmlinuz-$KERNELRELEASE
 	%endif
-$M	$MAKE %{?_smp_mflags} KERNELRELEASE=$KERNELRELEASE INSTALL_MOD_PATH=%{buildroot} modules_install
-	$MAKE %{?_smp_mflags} KERNELRELEASE=$KERNELRELEASE INSTALL_HDR_PATH=%{buildroot}/usr headers_install
+$M	$MAKE %{?_smp_mflags} INSTALL_MOD_PATH=%{buildroot} modules_install
+	$MAKE %{?_smp_mflags} INSTALL_HDR_PATH=%{buildroot}/usr headers_install
 	cp System.map %{buildroot}/boot/System.map-$KERNELRELEASE
 	cp .config %{buildroot}/boot/config-$KERNELRELEASE
 $S$M	rm -f %{buildroot}/lib/modules/$KERNELRELEASE/build