init_oss_soundcore() compares returned value of register_chrdev()
with -1, while other error codes can be returned.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: NAlexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>