Let boot(8) refer to the uart(4) serial driver, which is the replacement

for the obsolete sio(4) driver.

PR:             docs/144498
Submitted by:   Bruce Cran (bruce at cran dot org dot uk)
Approved by:    marcel
MFC after:      2 weeks

sbin/reboot/boot_i386.8

@@ -36,7 +36,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 18, 2005
+.Dd July 4, 2010
 .Dt BOOT 8 i386
 .Os
 .Sh NAME
@@ -220,14 +220,14 @@ you can use the
 option to force the kernel to use the serial port as its
 console device.
 The serial port driver
-.Xr sio 4
+.Xr uart 4
 has a flag (0x20) to override this option.
 If that flag is set, the serial port will always be used as the console,
 regardless of the
 .Fl h
 option described here.
 See the man page for
-.Xr sio 4
+.Xr uart 4
 for more details.
 .It Fl m
 mute the console to suppress all console input and output during the