PCI: vmd: Remove usage of the deprecated ida_simple_xx() API

ida_alloc() and ida_free() should be preferred to the deprecated
ida_simple_get() and ida_simple_remove().

This is less verbose.

Link: https://lore.kernel.org/linux-pci/270f25cdc154f3b0309e57b2f6421776752e2170.1702230593.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>