Revert "fdt: Fix fdtdec_get_addr_size() for 64-bit"

This reverts commit 5b344360.

This function has a few problems. It calls fdt_parent_offset() which as
mentioned in code review is very slow.

https://patchwork.ozlabs.org/patch/499482/
https://patchwork.ozlabs.org/patch/452604/



It also happens to break SPI flash on Minnowboard max which is how I noticed
that this was applied. I can send a patch to tidy that up, but in any case
I think we should consider a revert until the function is better implemented.

Signed-off-by: Simon Glass <sjg@chromium.org>