sound/oss/ac97_codec.c: restore MODULE_LICENSE

I accidentally removed the module license from sound/oss/ac97_codec.c in
commit 83bad1d764b836a482b88e0a1f44d7a5c3e1fee0 ("scheduled OSS driver
removal")

Spotted by Roland <devzero@web.de>.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

sound/oss/ac97_codec.c

@@ -1202,3 +1202,5 @@ static int pt101_init(struct ac97_codec * codec)
 
 EXPORT_SYMBOL(ac97_probe_codec);
 
+MODULE_LICENSE("GPL");
+