vmci: fix panic due to freeing unallocated resources

vmci: fix panic due to freeing unallocated resources

Summary:
An error mapping PCI resources results in a panic due to unallocated
resources being freed up. This change puts the appropriate checks in
place to prevent the panic.

PR:		252445
Reported by:	Marek Zarychta <zarychtam@plan-b.pwste.edu.pl>
Tested by:	marcus
MFC after:	1 week
Sponsored by:	VMware

Test Plan:
Along with user testing, also simulated error by inserting a ENXIO
return in vmci_map_bars().

Reviewed by:	marcus
Subscribers:	imp
Differential Revision: https://reviews.freebsd.org/D32016