fdt: Remove duplicate code

fdt: Remove duplicate code

Commit 6d29cc7dcf2d ("fdt: Fixup only valid memory banks") ended up
being merged twice, first as:

	commit 6d29cc7dcf2d35966aa0b6119fd1cbca0d21d5e6
	Author:     Thierry Reding <treding@nvidia.com>
	AuthorDate: Tue Jan 30 11:34:17 2018 +0100
	Commit:     Simon Glass <sjg@chromium.org>
	CommitDate: Sun Feb 18 12:53:38 2018 -0700

	    fdt: Fixup only valid memory banks

	    Memory banks with address 0 and size 0 are empty and should not be
	    passed to the OS via device tree.

	    Signed-off-by: Thierry Reding <treding@nvidia.com>
	    Acked-by: Stephen Warren <swarren@nvidia.com>
and later again, though this time it was v2:

	commit ed5af03f9bb8905f1e94d68ab49f22d7f061d75f
	Author:     Thierry Reding <treding@nvidia.com>
	AuthorDate: Thu Feb 15 19:05:59 2018 +0100
	Commit:     Tom Rini <trini@konsulko.com>
	CommitDate: Fri Feb 23 10:40:50 2018 -0500

	    fdt: Fixup only valid memory banks

	    Memory banks with address 0 and size 0 are empty and should not be
	    passed to the OS via device tree.

	    Acked-by: Stephen Warren <swarren@nvidia.com>
	    Signed-off-by: Thierry Reding <treding@nvidia.com>
The second version was slightly different, so the main hunk of the patch
was applied twice. This isn't harmful because the code is idempotent,
but it's wasteful to run the same code twice.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>