ALSA: pcm: Add missing error checks in OSS emulation plugin builder

commit 6708913750344a900f2e73bfe4a4d6dbbce4fe8d upstream.

In the OSS emulation plugin builder where the frame size is parsed in
the plugin chain, some places miss the possible errors returned from
the plugin src_ or dst_frames callback.

This patch papers over such places.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>