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/drivers/Kconfig b/sound/drivers/Kconfig
index 8545da9..0e3dc80 100644
--- a/sound/drivers/Kconfig
+++ b/sound/drivers/Kconfig
@@ -12,6 +12,17 @@
 	select SND_TIMER
 	select SND_HWDEP
 
+# select SEQ stuff to min(SND_SEQUENCER,SND_XXX)
+config SND_OPL3_LIB_SEQ
+	def_tristate SND_SEQUENCER && SND_OPL3_LIB
+	select SND_SEQ_MIDI_EMUL
+	select SND_SEQ_MIDI_EVENT
+
+config SND_OPL4_LIB_SEQ
+	def_tristate SND_SEQUENCER && SND_OPL4_LIB
+	select SND_SEQ_MIDI_EMUL
+	select SND_SEQ_MIDI_EVENT
+
 config SND_VX_LIB
 	tristate
 	select FW_LOADER
@@ -99,6 +110,8 @@
 	depends on SND_SEQUENCER
 	select SND_TIMER
 	select SND_RAWMIDI
+	select SND_SEQ_VIRMIDI
+	select SND_SEQ_MIDI_EVENT
 	help
 	  Say Y here to include the virtual MIDI driver.  This driver
 	  allows to connect applications using raw MIDI devices to