Makefile: distclean configure, rpm and source tar files

Remove the configure script, rpm files and .tar.gz source file when
running "make distclean". For "make clean", keep the configure script.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Makefile.am

@@ -29,3 +29,6 @@ rpm:
 	@echo "Building RPM packages requires rpmbuild and rpm utilities"
 	exit 1
 endif
+
+CLEANFILES = *.rpm *.tar.gz
+DISTCLEANFILES = *.rpm *.tar.gz configure