vulkan: move driver::Debuggable

Move it from loader.cpp to driver.cpp.  No functional change.

Change-Id: I455e798d6001f9719d378ae0295f2b4b181b0c09
diff --git a/vulkan/libvulkan/Android.mk b/vulkan/libvulkan/Android.mk
index e60d74c..665d45e 100644
--- a/vulkan/libvulkan/Android.mk
+++ b/vulkan/libvulkan/Android.mk
@@ -43,6 +43,7 @@
 	api_gen.cpp \
 	debug_report.cpp \
 	dispatch_gen.cpp \
+	driver.cpp \
 	layers_extensions.cpp \
 	loader.cpp \
 	swapchain.cpp \