tiny-printf: Adjust to avoid using data section

tiny-printf: Adjust to avoid using data section

We can pass all the variables down to the functions that need them, and
then everything is on the stack. This is safer than using the data section.

At least on firefly-rk3288, the code size is the same and the data size is
12 bytes smaller:

before:
  18865	   2636	     40	  21541	   5425	b/firefly-rk3288/spl/u-boot-spl
after:
  18865	   2624	     40	  21529	   5419	b/firefly-rk3288/spl/u-boot-spl

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Stefan Roese <sr@denx.de>