[target]: Add code to get LINUX_MACHTYPE by calling a function for all targets

Add code to read the hardware platform and return the corresponding
LINUX_MACHTYPE for msm7630_surf target.
diff --git a/makefile b/makefile
index 47ccb38..5773c58 100644
--- a/makefile
+++ b/makefile
@@ -28,6 +28,7 @@
 BOOTLOADER_OUT := .
 endif
 
+LK_TOP_DIR:= .
 BUILDDIR := $(BOOTLOADER_OUT)/build-$(PROJECT)
 OUTBIN := $(BUILDDIR)/lk.bin
 OUTELF := $(BUILDDIR)/lk