commonlib/include: remove NEED_VB20_INTERNALS

vboot_handoff.c is the only place that needs the vb2 internals.
Provide it in the one place it is actually required instead of
pulling in the headers unnecessarily in common code. There is,
however, still a need to get the vb2 hashing types for a function
declaration.

Change-Id: I038fda68b1cd05fa2e66135158e5e2d18567563a
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17475
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/commonlib/include/commonlib/cbfs.h

@@ -18,8 +18,6 @@
 
 #include <commonlib/cbfs_serialized.h>
 #include <commonlib/region.h>
-/* TODO: remove me! This is for vboot_handoff.c's benefit. */
-#define NEED_VB20_INTERNALS
 #include <vb2_api.h>
 
 /* Object representing cbfs files. */