ALSA: oss-mixer - use strlcpy() instead strcpy()

This is mostly a static checker fix more than anything else.  We're
copying from a 64 char buffer into a 44 char buffer.

The 64 character buffer is str[] in snd_mixer_oss_build_test_all().
The call tree is:
	snd_mixer_oss_build_test_all()
	-> snd_mixer_oss_build_test()
	   -> snd_mixer_oss_build_test().

We never actually do fill str[] buffer all the way to 64 characters.
The longest string is:
	sprintf(str, "%s Playback Switch", ptr->name);
ptr->name is a 32 character buffer so 32 plus 16 characters for
" Playback Switch" still puts us over the 44 limit from "id.name".

Most likely ptr->name never gets filled to the limit, but we can't
really change the size of that buffer so lets just use strlcpy() here
and be safe.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>