asm-generic/io.h: Fix !CONFIG_GENERIC_IOMAP pci_iounmap() implementation

asm-generic/io.h: Fix !CONFIG_GENERIC_IOMAP pci_iounmap() implementation

For arches that do not select CONFIG_GENERIC_IOMAP, the current
pci_iounmap() function does nothing causing obvious memory leaks
for mapped regions that are backed by MMIO physical space.

In order to detect if a mapped pointer is IO vs MMIO, a check must made
available to the pci_iounmap() function so that it can actually detect
whether the pointer has to be unmapped.

In configurations where CONFIG_HAS_IOPORT_MAP && !CONFIG_GENERIC_IOMAP,
a mapped port is detected using an ioport_map() stub defined in
asm-generic/io.h.

Use the same logic to implement a stub (ie __pci_ioport_unmap()) that
detects if the passed in pointer in pci_iounmap() is IO vs MMIO to
iounmap conditionally and call it in pci_iounmap() fixing the issue.

Leave __pci_ioport_unmap() as a NOP for all other config options.

Tested-by: George Cherian <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]
Link: https://lore.kernel.org/lkml/[email protected]
Link: https://lore.kernel.org/r/a9daf8d8444d0ebd00bc6d64e336ec49dbb50784.1600254147.git.lorenzo.pieralisi@arm.com
Reported-by: George Cherian <[email protected]>
Signed-off-by: Lorenzo Pieralisi <[email protected]>
Signed-off-by: Lorenzo Pieralisi <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: George Cherian <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Yang Yingliang <[email protected]>