zynq: Move SPL console init out of board_init_f()

We should not init the console this early since it precludes using driver
model for the UART, since it is not set up at the start of board_init_f().
See the README for more information. The debug UART does not have this
restriction. If we want to do early init with the console on it can be done
in spl_board_init().

Move the preloader_console_init() call from board_init_f() to board_init_r().

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>