rbutil: Merge rbutil with utils folder.

rbutil uses several components from the utils folder, and can be
considered part of utils too. Having it in a separate folder is an
arbitrary split that doesn't help anymore these days, so merge them.

This also allows other utils to easily use libtools.make without the
need to navigate to a different folder.

Change-Id: I3fc2f4de19e3e776553efb5dea5f779dfec0dc21

utils/mkimxboot/dualboot/dualboot.lds

@@ -0,0 +1,17 @@
+ENTRY(start)
+OUTPUT_FORMAT(elf32-littlearm)
+OUTPUT_ARCH(arm)
+
+MEMORY
+{
+    OCRAM : ORIGIN = 0, LENGTH = 0x8000
+}
+
+SECTIONS
+{
+    .text 0 :
+    {
+        *(.start*)
+        *(.text*)
+    } > OCRAM
+}