ALSA: hda - Fix oops caused by recent commit "Fix internal mic for Lenovo Ideapad U300s"

commit 83b0c6ba999643ee8ad6329f26e1cdc870e1a920 upstream.

Make sure we don't dereference the "quirk" pointer when it is null.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Weng Meiling <wengmeiling.weng@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>