bus/pci: fix TOCTOU for sysfs access

bus/pci: fix TOCTOU for sysfs access

Using access followed by open causes a static analysis warning
about Time of check versus Time of use. Also, access() and
open() have different UID permission checks.

This is not a serious problem; but easy to fix by using errno instead.

Coverity issue: 300870
Fixes: 4a928ef9f611 ("bus/pci: enable write combining during mapping")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: David Marchand <david.marchand@redhat.com>