PCI: Fix issue with "pci=disable_acs_redir" parameter being ignored

In most cases, kmalloc() will not be available early in boot when
pci_setup() is called.  Thus, the kstrdup() call that was added to fix the
__initdata bug with the disable_acs_redir parameter usually returns NULL,
so the parameter is discarded and has no effect.

To fix this, store the string that's in initdata until an initcall function
can allocate the memory appropriately.  This way we don't need any
additional static memory.

Fixes: d2fd6e81 ("PCI: Fix __initdata issue with "pci=disable_acs_redir" parameter")
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>