uboot-imx

Make printf and vprintf safe from buffer overruns

From: Sonny Rao <sonnyrao@chromium.org>

utilize the added vscnprintf functions to avoid buffer overruns
The implementation is fairly dumb in that it doesn't detect
that the buffer is too small, but at least will not cause crashes.

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>