staging: fix intel_sst/intelmid sound build

SND_INTELMID selects 3 SND_* kconfig symbols, but that is useless
if the SOUND & SND symbols in their hierarchy are not enabled,
so make this symbol depend on SOUND & SND.

ERROR: "snd_pcm_period_elapsed" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_card_create" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_hw_constraint_integer" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_device_new" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_set_ops" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_jack_new" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_lib_free_pages" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_lib_ioctl" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_lib_malloc_pages" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_ctl_new1" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_lib_preallocate_pages_for_all" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_card_free" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_card_register" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_jack_report" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_pcm_new" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!
ERROR: "snd_ctl_add" [drivers/staging/intel_sst/snd-intelmid.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>