armv8: spl: Call board_init_r from crt0_64 in SPL

armv8: spl: Call board_init_r from crt0_64 in SPL

As part of the startup process for boards using the SPL, the
meaning of board_init_f changed such that it should return normally
rather than calling board_init_r directly. (see
db910353a126d84fe8dff7a694ea792f50fcfb6a )
This was fixed in 32-bit arm, but broke when SPL was added to
64 bit arm. This fixes crt0_64 so that it calls board_init_r
during the SPL and removes the direct call from board_init_f
from the arm SPL example.

Signed-off-by: Jeremy Hunt <Jeremy.Hunt@DEShawResearch.com>
Acked-by: Simon Glass <sjg@chromium.org>