ia64: Remove redundant valid_mmap_phys_addr_range() from pci_mmap_page_range()

We know we are within a valid MMIO BAR by the time this function gets
called; there's no need to check.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Tony Luck <tony.luck@intel.com>