ALSA: core: Build conditionally and remove superfluous ifdefs

Minor cleanups of Makefile to build some codes conditionally so that
a few ifdefs can be reduced.

Acked-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --cc sound/core/Makefile
Simple merge

diff --cc sound/core/info.c
Simple merge

diff --cc sound/core/info_oss.c
Simple merge

diff --cc sound/core/seq/Makefile
Simple merge

diff --cc sound/core/seq/seq_info.c
Simple merge

diff --cc sound/core/sound_oss.c
Simple merge