gitignore: ignore debian build directory

Have git ignore the Debian directory created when running:
	make deb-pkg
Signed-off-by: Greg Dietsche <Gregory.Dietsche@cuw.edu>
Signed-off-by: Michal Marek <mmarek@suse.cz>

.gitignore

@@ -45,6 +45,11 @@ modules.builtin
 /Module.markers
 /Module.symvers
 
+#
+# Debian directory (make deb-pkg)
+#
+/debian/
+
 #
 # git files that we don't want to ignore even it they are dot-files
 #