staging: speakup: i18n.c: Change return type from int to bool

The possible return values (0 or 1) for compare_specifiers
and fmt_validate represent whether a condition holds or not, so
conceptually, they are booleans.

Update documentation for these two functions.

Change type of variable 'still_comparing' from int to bool too,
inside fmt_validate, because it is intended to hold truth values
as well.

Signed-off-by: Narcisa Ana Maria Vasile <narcisaanamaria12@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>