serial: 8250_port: simplify serial8250_request_std_resource()

Return immediately from the error locations or switch-case ends. It is
therefore easier to see the flow.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250317070046.24386-31-jirislaby@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>