PCI: make pcie_get_readrq visible in pci.h

[PATCH] PCI: make pcie_get_readrq visible in pci.h

pcie_get_readrq() is EXPORT_SYMBOL'ed, but its prototype is not
visible in pci.h, add it there.

This is needed by some network drivers.

Signed-off-by: Brice Goglin <brice@myri.com>
Acked-by: Peter Oruba <peter.oruba@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>