pxeboot(8): remove antiquated information

While I was there:
- Fix some typos
- Fix an excessive argument "indent" reported by mandoc -Tlint
- Replace a dead link with the one suggested by
  https://www.uefi.org/uefi

Submitted by:	linimon (in part)
Reviewed by:	bcr
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D27774

stand/i386/pxeldr/pxeboot.8

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd November 25, 2018
+.Dd February 15, 2021
 .Dt PXEBOOT 8
 .Os
 .Sh NAME
@@ -97,19 +97,19 @@ from the specified server before loading any other files.
 .Pp
 Valid
 .Va option root-path
-Syntax is the following
+syntax is the following
-.Bl -tag -width <scheme>://ip/path indent
+.Bl -tag -width <scheme>://ip/path
 .It /path
 path to the root filesystem on the NFS server
-.It ip:/path
+.It ip://path
 path to the root filesystem on the NFS server
 .Ar ip
-.It nfs:/path
+.It nfs://path
 path to the root filesystem on the NFS server
 .It nfs://ip/path
 path to the root filesystem on the NFS server
 .Ar ip
-.It tftp:/path
+.It tftp://path
 path to the root filesystem on the TFTP server
 .It tftp://ip/path
 path to the root filesystem on the TFTP server
@@ -129,18 +129,9 @@ In all other respects,
 acts just like
 .Xr loader 8 .
 .Pp
-As PXE is still in its infancy, some firmware versions may not work
-properly.
-The
-.Nm
-bootloader has been extensively tested on version 0.99 of Intel firmware;
-pre-release versions of the newer 2.0 firmware are known to have
-problems.
-Check with the device's manufacturer for their latest stable release.
-.Pp
 For further information on Intel's PXE specifications and Wired for
 Management (WfM) systems, see
-.Li http://www.intel.com/design/archives/wfm/ .
+.Li http://www.pix.net/software/pxeboot/archive/pxespec.pdf .
 .Sh SEE ALSO
 .Xr loader 8
 .Sh HISTORY