ACPI: PCI: update kernel-doc line comments

Update kernel-doc line comments to fix warnings reported by make W=1:

drivers/acpi/pci_root.c:71: warning: Function parameter or
member 'handle' not described in 'acpi_is_root_bridge'

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>