gitignore: added kconfig names

Add the lines from the .gitignore found in bst-kconfig. As in the
previous commit, use bst-kconfig commit v2.6.34-4-g8168c0b

(cherry-picked from wrpc-sw d923523a)

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

.gitignore

@@ -6,3 +6,10 @@ ppsi.bin
 *~
 /ppsi
 
+*.cmd
+*.o
+.tmp_*
+.config
+.config.old
+include/config
+include/generated