PCI: vmd: Update type of the __iomem pointers

PCI: vmd: Update type of the __iomem pointers

Use "void __iomem" instead "char __iomem" pointer type when working with
the accessor functions (with names like readb() or writel(), etc.) to
better match a given accessor function signature where commonly the address
pointing to an I/O memory region would be a "void __iomem" pointer.

Related: https://lwn.net/Articles/102232/

Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20201129230743.3006978-5-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jon Derrick <jonathan.derrick@intel.com>