[ALSA] Add SPI devices to ALSA Kconfig and Makefile

This patch adds SPI devices in the ALSA diretory, including the Kconfig and
Makefile.

Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/spi/Kconfig b/sound/spi/Kconfig
new file mode 100644
index 0000000..60fbb2a
--- /dev/null
+++ b/sound/spi/Kconfig
@@ -0,0 +1,6 @@
+#SPI drivers
+
+menu "SPI devices"
+	depends on SND != n
+
+endmenu