kbuild: deb-pkg: add --source-option=-sP

If the source package fails to build, ../linux.orig is left over.
In the next run of 'make deb-pkg', you will get the following error:

  dpkg-source: error: orig directory 'linux.orig' already exists, not overwriting, giving up; use -sA, -sK or -sP to override

You can manually remove ../linux.orig, but it is annoying.

Pass -sP down to dpkg-source.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.package

@@ -86,7 +86,7 @@ deb-pkg:
 	$(call cmd,src_tar,$(KDEB_SOURCENAME))
 	origversion=$$(dpkg-parsechangelog -SVersion |sed 's/-[^-]*$$//');\
 		mv $(KDEB_SOURCENAME).tar.gz ../$(KDEB_SOURCENAME)_$${origversion}.orig.tar.gz
-	+dpkg-buildpackage -r$(KBUILD_PKG_ROOTCMD) -a$$(cat debian/arch) $(DPKG_FLAGS) -i.git -us -uc
+	+dpkg-buildpackage -r$(KBUILD_PKG_ROOTCMD) -a$$(cat debian/arch) $(DPKG_FLAGS) --source-option=-sP -i.git -us -uc
 
 PHONY += bindeb-pkg
 bindeb-pkg: