PCI: fix range check on mmapped sysfs resource files

pci_mmap_fits() returns the wrong answer if the sysfs resource file size
is not a multiple of the page size.  vm_end and vm_start are already
page-aligned, so size - start < nr, causing mmap() to return EINVAL.

Signed-off-by: Ed Swierk <eswierk@aristanetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>