ice: enable VF admin queue interrupts

The VPINT_MBX_CTL register array must be programmed to enable VF admin
queue interrupts. Without this, VFs never get interrupts on vector 0,
and some VF drivers will fail to init.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>