hw/nvme: fix msix_uninit with exclusive bar

hw/nvme: fix msix_uninit with exclusive bar

Commit fa905f65c554 introduced a machine compatibility parameter to
enable an exclusive bar for msix. It failed to account for this when
cleaning up. Make sure that if an exclusive bar is enabled, we use the
proper cleanup routine.

Cc: qemu-stable@nongnu.org
Fixes: fa905f65c554 ("hw/nvme: add machine compatibility parameter to enable msix exclusive bar")
Reviewed-by: Jesper Wendel Devantier <foss@defmacro.it>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
(cherry picked from commit 9162f101257639cc4c7e20f72f77268b1256dd79)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>