ALSA: clean up the logic for building sequencer modules

Instead of mangling the CONFIG_* variables in the makefiles over and
over, set a few helper variables in Kconfig.

Signed-off-by: Michal Marek <mmarek@suse.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/synth/Makefile b/sound/synth/Makefile
index e99fd76..11eb06a 100644
--- a/sound/synth/Makefile
+++ b/sound/synth/Makefile
@@ -5,16 +5,8 @@
 
 snd-util-mem-objs := util_mem.o
 
-#
-# this function returns:
-#   "m" - CONFIG_SND_SEQUENCER is m
-#   <empty string> - CONFIG_SND_SEQUENCER is undefined
-#   otherwise parameter #1 value
-#
-sequencer = $(if $(subst y,,$(CONFIG_SND_SEQUENCER)),$(if $(1),m),$(if $(CONFIG_SND_SEQUENCER),$(1)))
-
 # Toplevel Module Dependency
 obj-$(CONFIG_SND_EMU10K1) += snd-util-mem.o
 obj-$(CONFIG_SND_TRIDENT) += snd-util-mem.o
-obj-$(call sequencer,$(CONFIG_SND_SBAWE)) += snd-util-mem.o
-obj-$(call sequencer,$(CONFIG_SND)) += emux/
+obj-$(CONFIG_SND_SBAWE_SEQ) += snd-util-mem.o
+obj-$(CONFIG_SND_SEQUENCER) += emux/