ovmf: fix gcc12 warning in GenFfs

ovmf: fix gcc12 warning in GenFfs

Backport [https://github.com/tianocore/edk2/commit/7b005f344e533cd913c3ca05b266f9872df886d1]

Fixes:

    GenFfs.c:545:5: error: pointer ?InFileHandle? used after ?fclose? [-Werror=use-after-free]
      545 |     Error(NULL, 0, 4001, "Resource", "memory cannot be allocated  of %s", InFileHandle);
          |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    GenFfs.c:544:5: note: call to ?fclose? here
      544 |     fclose (InFileHandle);
          |     ^~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Steve Sakoman <steve@sakoman.com>