kbuild: pkg: clean up package files/dirs from the top Makefile

I am not a big fan of the $(objtree)/ hack for clean-files/clean-dirs.

These are created in the top of $(objtree), so let's clean them up
from the top Makefile.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/Makefile b/Makefile
index db2ddd5..69cb3ec 100644
--- a/Makefile
+++ b/Makefile
@@ -1386,12 +1386,14 @@
 
 # Directories & files removed with 'make mrproper'
 MRPROPER_DIRS  += include/config include/generated          \
-		  arch/$(SRCARCH)/include/generated .tmp_objdiff
+		  arch/$(SRCARCH)/include/generated .tmp_objdiff \
+		  debian/ snap/ tar-install/
 MRPROPER_FILES += .config .config.old .version \
 		  Module.symvers \
 		  signing_key.pem signing_key.priv signing_key.x509	\
 		  x509.genkey extra_certificates signing_key.x509.keyid	\
-		  signing_key.x509.signer vmlinux-gdb.py
+		  signing_key.x509.signer vmlinux-gdb.py \
+		  *.spec
 
 # Directories & files removed with 'make distclean'
 DISTCLEAN_DIRS  +=