audio-kernel: Enable out of tree compilaton

Add Makefile in each sub-folder
Add Android.mk file on top level folder of audio-kernel

Change-Id: I024aa5080ae52b55700f0a65ab05034be8c9cdad
Signed-off-by: Jyotirmoi Sarma <jyosarma@codeaurora.org>

asoc/codecs/wsa883x/Makefile

@@ -0,0 +1,6 @@
+modules:
+	$(MAKE) -C $(KERNEL_SRC) M=$(M) modules $(KBUILD_OPTIONS) VERBOSE=1
+modules_install:
+	$(MAKE) M=$(M) -C $(KERNEL_SRC) modules_install
+clean:
+	$(MAKE) -C $(KERNEL_SRC) M=$(M) clean