exynos: enable serial output in SPL

With this change the Exynos SPL initializes serial interface and
provides a limited printf() support (maximum line length not to exceed
150 characters).

Serial driver wrapper uses default serial console when in SPL.

BRANCH=none
BUG=none
TEST=manual

   . added a printf() statement in lowlevel_init.c, built and ran pit
     image. Observed

     do_lowlevel_init:282 all initialized!

     printed on the console when SPL started.

Change-Id: I6730c49404c2a2bebcb98d5749396d578e853de3
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/61484
5 files changed