Documentation: PM: Fix PCI hibernation support description

According to the context, 'pci_pm_suspend_noirq' is the right
word for the changed sentence.

Signed-off-by: Yiwei Lin <s921975628@gmail.com>
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>