Fix do_div() usage in nand process output

Fix usage of do_div() in nand erase|read|write process output.

The last patch to nand_util.c introduced do_div() instead of libgcc's
implementation. But do_div() returns the quotient in its first
macro parameter and not as result.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd-electronics.com>