usb: xhci: cleanup xhci_hub_report_usb3_link_state()

usb: xhci: cleanup xhci_hub_report_usb3_link_state()

Improve readability of xhci_hub_report_usb3_link_state().

Comments are shortened and clarified, and the code now makes it explicit
when the Port Link State (PLS) value is modified versus when other status
bits are updated.

No functional changes.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20260402131342.2628648-22-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>