tools/nolibc/printf: Use goto and reduce indentation

tools/nolibc/printf: Use goto and reduce indentation

Upcoming changes will need to use goto to jump to the code that
outputs characters.
Use 'goto do_output' to output a known number of characters.
Use 'goto do_strlen_output' to output a '\0' terminated string.

Removes a level of indentation from the format processing code.

The change is best reviewed using 'git diff -b' after applying it.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260308113742.12649-8-david.laight.linux@gmail.com
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>