ALSA: seq: Reorganize kconfig and build

This is a slightly intensive rewrite of Kconfig and Makefile about
ALSA sequencer stuff.

The first major change is that the kconfig items for the sequencer are
moved to sound/core/seq/Kconfig.  OK, that's easy.

The substantial change is that, instead of hackish top-level module
selection in Makefile, we define a Kconfig item for each sequencer
module.  The driver that requires such sequencer components select
exclusively the kconfig items.  This is more straightforward and
standard way.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/Kconfig b/sound/pci/Kconfig
index 32151d8..bc7acb4 100644
--- a/sound/pci/Kconfig
+++ b/sound/pci/Kconfig
@@ -477,6 +477,12 @@
 	  To compile this driver as a module, choose M here: the module
 	  will be called snd-emu10k1.
 
+# select SEQ stuff to min(SND_SEQUENCER,SND_XXX)
+config SND_EMU10K1_SEQ
+	def_tristate SND_SEQUENCER && SND_EMU10K1
+	select SND_SEQ_MIDI_EMUL
+	select SND_SEQ_VIRMIDI
+
 config SND_EMU10K1X
 	tristate "Emu10k1X (Dell OEM Version)"
 	select SND_AC97_CODEC