mana: fix a KASSERT panic on recursed lock access in mana_cfg_vport

The panic stack looks like this:
panic: _sx_xlock_hard: recursed on non-recursive sx MANA port lock
@ /usr/src/sys/dev/mana/mana_en.c:1022

KDB: stack backtrace:
vpanic() at vpanic+0x150/frame 0xfffffe011b3c1970
panic() at panic+0x43/frame 0xfffffe011b3c19d0
_sx_xlock_hard() at _sx_xlock_hard+0x82d/frame 0xfffffe011b3c1a70
_sx_xlock() at _sx_xlock+0xb0/frame 0xfffffe011b3c1ab0
mana_cfg_vport() at mana_cfg_vport+0x79/frame 0xfffffe011b3c1b40
mana_alloc_queues() at mana_alloc_queues+0x3b/frame 0xfffffe011b3c1c50
mana_up() at mana_up+0x40/frame 0xfffffe011b3c1c70
mana_ioctl() at mana_ioctl+0x25b/frame 0xfffffe011b3c1cb0
ifhwioctl() at ifhwioctl+0xd11/frame 0xfffffe011b3c1db0
hn_xpnt_vf_init() at hn_xpnt_vf_init+0x15f/frame 0xfffffe011b3c1e10

The lock has already been held in the caller. Remove this
redundant lock attempt.

Reported by: NetApp
Sponsored by: Microsoft