bnxt: add 400GBase-FR4 support

[gallatin]

Summary

Support 400GBase-FR4 optics, allowing the driver to report
"Ethernet autoselect (400GBase-FR4 <full-duplex>)" for FR4
media

Test Plan

Note this change depends on https://reviews.freebsd.org/D61135 / 0e44056f19ab if_media: Add 400G FR4 media types to test
Note also that ifconfig must be rebuilt using the above to see FR4 meda.

• Insert 400G FR4 media in a Broadcom Thor2 device, observe media is correctly reported. Eg:

# ifconfig -v net0
net0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
	options=1ee507bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6,HWSTATS,HWRXTSTMP,MEXTPG,TXTLS4,TXTLS6>
	ether 8c:84:74:05:dd:9a
	media: Ethernet autoselect (400GBase-FR4 <full-duplex>)
	status: active
	nd6 options=829<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL,STABLEADDR>
	drivername: bnxt0
	plugged: QSFP+(CMIS) 400G-FR4/400GBASE-FR4 (LC)
	vendor: FLEXOPTIX PN: Q.164HG.2.C SN: F7Z5BVD DATE: 2025-08-22
	module temperature: 57.28 C voltage: 3.26 Volts
	lane 1: RX power: 1.57 mW (1.96 dBm) TX bias: 75.10 mA
	lane 2: RX power: 1.53 mW (1.86 dBm) TX bias: 85.00 mA
	lane 3: RX power: 1.30 mW (1.15 dBm) TX bias: 74.82 mA
	lane 4: RX power: 1.47 mW (1.66 dBm) TX bias: 85.89 mA