MdeModulePkg/Setup: Update opcode number variable type to UINTN

MdeModulePkg/Setup: Update opcode number variable type to UINTN

Update data type of variables which save the opcode numbers
to UINTN, in case some configuration module has lots of
configuration items.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Signed-off-by: Brian R Haug <brian.r.haug@intel.com>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>