sdm845: add common sdm845 lunch target

This target builds a "generic" sdm845 device which should boot on all
SDM845 devices with common boot, vendor and system images.
diff --git a/Android.mk b/Android.mk
index d54b34d..32fa53c 100644
--- a/Android.mk
+++ b/Android.mk
@@ -20,7 +20,7 @@
 # to only building on ARM if they include assembly. Individual makefiles
 # are responsible for having their own logic, for fine-grained control.
 
-ifneq ($(filter enchilada beryllium, $(TARGET_BOARD_PLATFORM)),)
+ifneq ($(filter enchilada beryllium sdm845, $(TARGET_BOARD_PLATFORM)),)
 
 LOCAL_PATH := $(call my-dir)