PCI: Add devres helpers for iomap table

The pcim_iomap_devres.table administrated by pcim_iomap_table() has its
entries set and unset at several places throughout devres.c using manual
iterations which are effectively code duplications.

Add pcim_add_mapping_to_legacy_table() and
pcim_remove_mapping_from_legacy_table() helper functions and use them where
possible.

Link: https://lore.kernel.org/r/20240613115032.29098-3-pstanner@redhat.com


Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>