x86: Do relocation before clearing BSS

x86: Do relocation before clearing BSS

The BSS region may overlap with relocations. If we clear BSS we will
overwrite the start of the relocation area. This doesn't matter when running
from SPI flash, since it is read-only. But when relocating 64-bit U-Boot
from one place in RAM to another, relocation will fail because some of its
relocations have been zeroed.

To fix this, put the ELF fixup call before the BSS clearing call.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>