ifconfig: Fix the display of the IFCAP_MEXTPG capability without netlink

Historically this capability is IFCAP_NOMAP but it was renamed to
IFCAP_MEXTPG. Catch up with the change 3f43ada98c89.

PR: 289545
Fixes: 3f43ada98c89 Catch up with 6edfd179c86: mechanically rename IFCAP_NOMAP to IFCAP_MEXTPG
MFC after: 3 days

(cherry picked from commit 5017fdb728811fd3e15d7151524378f49a49aee1)
(cherry picked from commit 5f472754ba6f9cc95607956c6e2ad6483c9dd157)