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>

sound/isa/sb/Makefile

@@ -13,14 +13,6 @@ snd-sbawe-objs := sbawe.o emu8000.o
 snd-emu8000-synth-objs := emu8000_synth.o emu8000_callback.o emu8000_patch.o emu8000_pcm.o
 snd-es968-objs := es968.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-$(CONFIG_SND_SB_COMMON) += snd-sb-common.o
 obj-$(CONFIG_SND_SB16_DSP) += snd-sb16-dsp.o
@@ -33,4 +25,4 @@ ifeq ($(CONFIG_SND_SB16_CSP),y)
   obj-$(CONFIG_SND_SB16) += snd-sb16-csp.o
   obj-$(CONFIG_SND_SBAWE) += snd-sb16-csp.o
 endif
-obj-$(call sequencer,$(CONFIG_SND_SBAWE)) += snd-emu8000-synth.o
+obj-$(CONFIG_SND_SBAWE_SEQ) += snd-emu8000-synth.o