linux-user: Return void from queue_signal()

linux-user: Return void from queue_signal()

The linux-user queue_signal() function always returns 1, and none of
its callers check the return value.  Give it a void return type
instead.

The return value is a leftover from the old pre-2016 linux-user
signal handling code, which really did have a queue of signals and so
might return a failure indication if too many signals were queued at
once.  The current design avoids having to ever have more than one
signal queued via queue_signal() at once, so it can never fail.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220114153732.3767229-4-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>