ALSA Makefile cleanup: use $(mod-subdirs)

Some places were doing:

        subdir-$(CONFIG_FOO) += foo
        ifeq ($(CONFIG_FOO),y)
          subdir-m += foo
        fi

That can be expressed more easily as

        mod-subdirs := foo
        subdir-$(CONFIG_FOO) += foo

sound/Makefile

@@ -5,21 +5,17 @@ O_TARGET := sound.o
 
 export-objs     := sound_core.o
 
+mod-subdirs	:= oss core i2c drivers isa pci ppc synth
+
 obj-$(CONFIG_SOUND) += soundcore.o
 
 subdir-$(CONFIG_SOUND_PRIME) += oss
-
 ifeq ($(CONFIG_SOUND_PRIME),y)
-  subdir-m += oss
   obj-y += oss/sounddrivers.o
 endif
 
-_subdirs := core i2c drivers isa pci ppc arm synth
-
-subdir-$(CONFIG_SND) += $(_subdirs)
-
+subdir-$(CONFIG_SND) += core i2c drivers isa pci ppc arm synth
 ifeq ($(CONFIG_SND),y)
-  subdir-m += $(_subdirs)
   obj-y += core/core.o i2c/_i2c.o
   obj-y += drivers/drivers.o \
 	   drivers/mpu401/_mpu401.o \

sound/core/Makefile

@@ -7,6 +7,8 @@ O_TARGET     := core.o
 
 export-objs  := sound.o pcm.o pcm_lib.o rawmidi.o timer.o rtctimer.o hwdep.o
 
+mod-subdirs  := oss seq
+
 snd-objs     := sound.o init.o isadma.o memory.o info.o control.o misc.o \
                 device.o wrappers.o
 ifeq ($(CONFIG_SND_OSSEMUL),y)
@@ -31,7 +33,6 @@ obj-$(CONFIG_SND_HWDEP) += snd-hwdep.o
 subdir-$(CONFIG_SND_MIXER_OSS) += oss
 subdir-$(CONFIG_SND_PCM_OSS) += oss
 ifeq ($(filter $(subdir-y),oss),oss)
-  subdir-m += oss
   obj-y += oss/oss.o
 endif
 
@@ -39,7 +40,6 @@ obj-$(CONFIG_SND_PCM_OSS) += snd-pcm.o
 
 subdir-$(CONFIG_SND_SEQUENCER) += seq
 ifeq ($(CONFIG_SND_SEQUENCER),y)
-  subdir-m += seq
   obj-y += seq/sq.o
 endif
 

sound/core/seq/Makefile

@@ -5,9 +5,11 @@
 
 O_TARGET     := sq.o
 
+mod-subdirs  := instr
+
 subdir-y     := instr
-subdir-m     := $(subdir-y)
 obj-y        += instr/instr.o
+
 subdir-$(CONFIG_SND_SEQUENCER_OSS) += oss
 ifeq ($(CONFIG_SND_SEQUENCER_OSS),y)
   obj-y	     += oss/oss.o

sound/drivers/Makefile

@@ -5,8 +5,9 @@
 
 O_TARGET     := drivers.o
 
+mod-subdirs  := opl3 mpu401
+
 subdir-y     := opl3 mpu401
-subdir-m     := $(subdir-y)
 
 snd-dummy-objs := dummy.o
 snd-mtpav-objs := mtpav.o

sound/isa/Makefile

@@ -5,8 +5,9 @@
 
 O_TARGET     := isa.o
 
+mod-subdirs  := ad1816a ad1848 cs423x es1688 gus opti9xx sb wavefront
+
 subdir-y     := ad1816a ad1848 cs423x es1688 gus opti9xx sb wavefront
-subdir-m     := $(subdir-y)
 
 snd-als100-objs := als100.o
 snd-azt2320-objs := azt2320.o

sound/pci/Makefile

@@ -5,8 +5,9 @@
 
 O_TARGET     := pci.o
 
+mod-subdirs  := ac97 ali5451 cs46xx emu10k1 korg1212 nm256 rme9652 trident ymfpci
+
 subdir-y     := ac97 ali5451 cs46xx emu10k1 korg1212 nm256 rme9652 trident ymfpci
-subdir-m     := $(subdir-y)
 
 snd-als4000-objs := als4000.o
 snd-cmipci-objs := cmipci.o

sound/synth/Makefile

@@ -5,8 +5,9 @@
 
 O_TARGET     := synth.o
 
+mod-subdirs  := emux
+
 subdir-y     := emux
-subdir-m     := $(subdir-y)
 
 export-objs  := util_mem.o