Use do_div from div64.h for vsprintf

Use do_div from div64.h for vsprintf in case of 64bit division.
For 32bit division, do_div from div64.h can't be used as it
needs a 64bit parameter.

Signed-off-by: Dirk Behme <dirk.behme@googlemail.com>
Acked-by: Stefan Roese <sr@denx.de>
CC: Simon Kagstrom <simon.kagstrom@netinsight.net>