CRAS: Add custom volume curve for stumpy/lumpy.

Add a volume curve for Stumpy and Lumpy that provides a wider range of
useful volumes.  This provides higher volume at lower slider levels.

BUG=chromium-os:25412
TEST=Boot stumpy/lumpy and watch "alsamixer -c0" volume slider relative
to the system volume.

Change-Id: Iaf1d41103ab6aad38c3dae256253c9a37356563f
diff --git a/Makefile b/Makefile
index 7da5c12..56e6e66 100644
--- a/Makefile
+++ b/Makefile
@@ -52,6 +52,20 @@
 
 endif
 
+optional_cras_conf := $(wildcard $(ADHD_DIR)/cras-config/$(BOARD)/*)
+
+ifneq ($(strip $(optional_cras_conf)),)
+
+.PHONY: cras-config-files
+cras-config-files:
+	$(ECHO) "Installing cras config files"
+	$(INSTALL) --mode 755 -d $(DESTDIR)etc/cras/
+	$(INSTALL) --mode 644 -D "$(optional_cras_conf)" $(DESTDIR)etc/cras/
+
+install:	cras-config-files
+
+endif
+
 install:	$(DESTDIR)/etc/init/cras.conf				\
 		$(DESTDIR)/etc/asound.state				\
 		$(DESTDIR)/usr/bin/gavd					\