usb: xhci: remove duplicate TRB_TO_SLOT_ID() calls

Remove unnecessary repeated calls to TRB_TO_SLOT_ID(). The slot ID is
stored in the 'slot_id' variable at the function's start.

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/20240429140245.3955523-18-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>