usb: xhci: make 'sbrn' a local variable

usb: xhci: make 'sbrn' a local variable

Variable 'sbrn' is used to store the Serial Bus Release Number, which is
then only used for a debug message. Thus, 'sbrn' can be a local variable
and assigned after the primary HCD check. The SBRN debug message is only
printed when a primary HCD is setup.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240905143300.1959279-8-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>