man ip-link: Add deleting links by group

Indicate possibility deleting virtual links by group.

Also changed the alignment of 'ip link delete' args
descriptions, to look like similary to 'ip link set'.
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

man/man8/ip-link.8.in

@@ -78,7 +78,10 @@ ip-link \- network device configuration
 .BR ipvlan " ]"
 
 .ti -8
-.BI "ip link delete " DEVICE
+.BR "ip link delete " {
+.IR DEVICE " | "
+.BI "group " GROUP
+}
 .BI type " TYPE"
 .RI "[ " ARGS " ]"
 
@@ -588,15 +591,19 @@ the following additional arguments are supported:
 - specifies the mode (datagram or connected) to use.
 
 .SS ip link delete - delete virtual link
-.I DEVICE
-specifies the virtual  device to act operate on.
-.I TYPE
-specifies the type of the device.
-
 
 .TP
 .BI dev " DEVICE "
-specifies the physical device to act operate on.
+specifies the virtual device to act operate on.
+
+.TP
+.BI group " GROUP "
+specifies the group of virtual links to delete. Group 0 is not allowed to be
+deleted since it is the default group.
+
+.TP
+.BI type " TYPE "
+specifies the type of the device.
 
 .SS ip link set - change device attributes