MdeModulePkg/UdfDxe: don't return unset Status if INLINE_DATA req succeeds

Ard reports that clang-3.8 correctly flags the following issue in the
ReadFile() function:

If "RecordingFlags" is INLINE_DATA, then there are three paths through the
code where we mean to return success, but forget to set Status
accordingly:

(1) when "ReadFileInfo->Flags" is READ_FILE_GET_FILESIZE, or

(2) when "ReadFileInfo->Flags" is READ_FILE_ALLOCATE_AND_READ and
    AllocatePool() succeeds, or

(3) when "ReadFileInfo->Flags" is READ_FILE_SEEK_AND_READ.

Set "Status" to EFI_SUCCESS when we are done processing the INLINE_DATA
request, i.e., when we reach the corresponding "break" statament under the
INLINE_DATA case label.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Paulo Alcantara <pcacjr@zytor.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Paulo Alcantara <pcacjr@zytor.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c

@@ -967,7 +967,9 @@ ReadFile (
       return EFI_INVALID_PARAMETER;
     }
 
+    Status = EFI_SUCCESS;
     break;
+
   case LONG_ADS_SEQUENCE:
   case SHORT_ADS_SEQUENCE:
     //