lttng libs: add Makefile

Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/lttng/lib/Makefile

+obj-m += lib-ring-buffer.o
+
+lib-ring-buffer-objs := \
+	ringbuffer/ring_buffer_backend.o \
+	ringbuffer/ring_buffer_frontend.o \
+	ringbuffer/ring_buffer_iterator.o \
+	ringbuffer/ring_buffer_vfs.o \
+	ringbuffer/ring_buffer_splice.o \
+	ringbuffer/ring_buffer_mmap.o \
+	prio_heap/lttng_prio_heap.o \
+	../wrapper/splice.o