PCI/P2PDMA: Simplify distance calculation

Merge __calc_map_type_and_dist() and calc_map_type_and_dist_warn() into
calc_map_type_and_dist() to simplify the code a bit.  This now means we add
the devfn strings to the acs_buf unconditionally even if the buffer is not
printed, but that is not a lot of overhead and keeps the code much simpler.

Link: https://lore.kernel.org/r/20210614055310.3960791-1-hch@lst.de


Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>