serial: introduce uart_port_lock() guard()s

Having this, guards like these work:
guard(uart_port_lock_irq)(&up->port);
or
scoped_guard(uart_port_lock_irqsave, port) {
...
}

See e.g. "serial: 8250: use guard()s" later in this series.

Signed-off-by: "Jiri Slaby (SUSE)" <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

include/linux/serial_core.h

···
 	spin_unlock_irqrestore(&up->lock, flags);
 }
 
+DEFINE_GUARD(uart_port_lock, struct uart_port *, uart_port_lock(_T), uart_port_unlock(_T));
+DEFINE_GUARD_COND(uart_port_lock, _try, uart_port_trylock(_T));
+
+DEFINE_GUARD(uart_port_lock_irq, struct uart_port *, uart_port_lock_irq(_T),
+	     uart_port_unlock_irq(_T));
+
+DEFINE_LOCK_GUARD_1(uart_port_lock_irqsave, struct uart_port,
+                    uart_port_lock_irqsave(_T->lock, &_T->flags),
+                    uart_port_unlock_irqrestore(_T->lock, _T->flags),
+                    unsigned long flags);
+DEFINE_LOCK_GUARD_1_COND(uart_port_lock_irqsave, _try,
+			 uart_port_trylock_irqsave(_T->lock, &_T->flags));
+
 static inline int serial_port_in(struct uart_port *up, int offset)
 {
 	return up->serial_in(up, offset);