MdeModulePkg/XhciDxe: fix a bug on TRB check in async int transfer

MdeModulePkg/XhciDxe: fix a bug on TRB check in async int transfer

The last TRB in transfer ring is a LINK type TRB, which shouldn't
be accounted as a valid item in IsAsyncIntTrb().

Without this fix, the original algo will bring issue on those URBs
whose TRBs crosses the transfer ring.

Cc: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Feng Tian <feng.tian@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>