usb: xhci: add PORTSC variable to xhci_hub_control()

usb: xhci: add PORTSC variable to xhci_hub_control()

The variable 'temp' is used multiple times throughout xhci_hub_control()
for holding only PORTSC register values.

As a follow-up to introducing a dedicated variable for PORTPMSC, rename
all remaining 'temp' to 'portsc'. This improves readability and clarifies
what is being modified.

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/20260402131342.2628648-20-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>