i40e: Use BIT() macro for priority map parsing

Replace one left over (1 << up) in the i40e_dcb.c file with the BIT()
macro.

Change-ID: I39492a400a2cee5ac566143a5b436cc478bea0db
Signed-off-by: Neerav Parikh <neerav.parikh@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>