tools/nolibc/printf: Change variables 'c' to 'ch' and 'tmpbuf[]' to 'outbuf[]'

tools/nolibc/printf: Change variables 'c' to 'ch' and 'tmpbuf[]' to 'outbuf[]'

Changing 'c' makes the code slightly easier to read because the variable
stands out from the single character literals (especially 'c').

Change tmpbuf[] to outbuf[] because 'out' points into it.

The following patches pretty much rewrite the function so the
churn is limited.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260223101735.2922-7-david.laight.linux@gmail.com
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>