rge: add Wake-on-LAN support for magic packet

Advertise IFCAP_WOL_MAGIC when PCI power management is available
and enable it by default.  On suspend or shutdown, rge_setwol()
enables the WOL_MAGIC and WOL_LANWAKE bits in CFG3/CFG5, disables
the RXDV gate, and enables PM so the NIC stays powered to watch
for magic packets.

Move hardware-specific WOL register configuration into
rge_wol_config() in if_rge_hw.c to keep hardware-specific
functions in sync with OpenBSD.

Update rge.4 to document WoL support.

Tested on FreeBSD 16.0-CURRENT bare metal with Realtek RTL8125
on a Gigabyte B650 Gaming X AX motherboard.

Signed-off-by: Christos Longros <chris.longros@gmail.com>

Reviewed by:	adrian
Differential Revision:	https://reviews.freebsd.org/D56259

share/man/man4/rge.4

@@ -3,7 +3,7 @@
 .\"
 .\" SPDX-License-Identifier: BSD-2-Clause
 .\"
-.Dd December 18, 2025
+.Dd April 5, 2026
 .Dt RGE 4
 .Os
 .Sh NAME
@@ -39,8 +39,8 @@ over CAT6 cable.
 .Pp
 All NICs supported by the
 .Nm
-driver have TCP/IP checksum offload and hardware VLAN tagging/insertion
-features, and use a descriptor-based DMA mechanism.
+driver have TCP/IP checksum offload, hardware VLAN tagging/insertion
+features, Wake On Lan (WOL), and use a descriptor-based DMA mechanism.
 They are also
 capable of TCP large send (TCP segmentation offload).
 .Pp