mpc5200: spl_boot.c: Change init oder to first enable printf

On MPC5200, the initial RAM (and gd) is located in the internal
SRAM. So we can actually call the preloader console init code
before calling initdram(). This makes serial output (printf)
available very early, even before SDRAM init, which has been
an U-Boot priciple from day 1.

Signed-off-by: Stefan Roese <sr@denx.de>