man4: remove references to gone eeprom(8) and obsolete devices

The former was missed in 702547720c and
r357794 respectively.
Additionally for dc.4 and gem.4, remove on-board and SBus devices whose
support was removed as part of 58aa35d429
and r357455 respectively.

share/man/man4/cas.4

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 24, 2012
+.Dd December 26, 2020
 .Dt CAS 4
 .Os
 .Sh NAME
@@ -110,7 +110,6 @@ Sun Quad GigaSwift Ethernet PCI-X (QGE-X)
 .Xr miibus 4 ,
 .Xr netintro 4 ,
 .Xr vlan 4 ,
-.Xr eeprom 8 ,
 .Xr ifconfig 8
 .Sh HISTORY
 The

share/man/man4/dc.4

@@ -30,7 +30,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 24, 2011
+.Dd December 26, 2020
 .Dt DC 4
 .Os
 .Sh NAME
@@ -199,9 +199,6 @@ Alfa Inc GFC2204 (ASIX AX88140A)
 Built in 10Mbps only Ethernet on Compaq Presario 7900 series
 desktops (21143, non-MII)
 .It
-Built in Sun DMFE 10/100 Mbps Ethernet on Sun Netra X1 and Sun Fire V100
-(DM9102A, MII)
-.It
 Built in Ethernet on LinkSys EtherFast 10/100 Instant GigaDrive (DM9102, MII)
 .It
 CNet Pro110B (ASIX AX88140A)
@@ -326,7 +323,6 @@ the card should be configured correctly.
 .Xr ng_ether 4 ,
 .Xr polling 4 ,
 .Xr vlan 4 ,
-.Xr eeprom 8 ,
 .Xr ifconfig 8
 .Rs
 .%T ADMtek AL981, AL983 and AL985 data sheets

share/man/man4/gem.4

@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 25, 2009
+.Dd December 26, 2020
 .Dt GEM 4
 .Os
 .Sh NAME
@@ -83,16 +83,12 @@ driver at this time:
 .It
 Sun Gigabit Ethernet PCI 2.0/3.0 (GBE/P)
 (part no.\& 501-4373)
-.It
-Sun Gigabit Ethernet SBus 2.0/3.0 (GBE/S)
-(part no.\& 501-4375)
 .El
 .Sh SEE ALSO
 .Xr altq 4 ,
 .Xr miibus 4 ,
 .Xr netintro 4 ,
 .Xr vlan 4 ,
-.Xr eeprom 8 ,
 .Xr ifconfig 8
 .Sh HISTORY
 The