When we match UARTs found during bus-enumeration with UARTs used for

system devices (i.e. console, debug port or keyboard), don't stop
after the first match. Find them all and keep track of the last.
The reason for this change is that the low-level console is always
added to the list of system devices first, with other devices added
later. Since new devices are added to the list at the head, we have
the console always at the end. When a debug port is using the same
UART as the console, we would previously mark the "newbus" UART as
a debug port instead of as a console. This would later result in a
panic because no "newbus" device was associated with the console.
By matching all possible system devices we would mark the "newbus"
UART as a console and not as a debug port.
While it is arguably better to be able to mark a "newbus" UART as
both console and debug port, this fix is lightweight and allows
a single UART to be used as the console as well as a debug port
with only the aesthetic bug of not telling the user about it also
being a debug port.

Now that we match all possible system devices, update the rclk of
the system devices with the rclk that was obtained through the
bus attachment. It is generally true that clock information is
more reliable when obtained from the parent bus than by means of
some hardcoded or assumed value used early in the boot. This by
virtue of having more context information.

MFC after: 1 month

sys/dev/uart/uart_core.c

@@ -344,7 +344,7 @@ uart_bus_probe(device_t dev, int regshft, int rclk, int rid, int chan)
 		    uart_cpu_eqres(&sc->sc_bas, &sysdev->bas)) {
 			/* XXX check if ops matches class. */
 			sc->sc_sysdev = sysdev;
-			break;
+			sysdev->bas.rclk = sc->sc_bas.rclk;
 		}
 	}