MdeModulePkg/UdfDxe: ASSERT() valid ReadFileInfo Flags for INLINE_DATA req

MdeModulePkg/UdfDxe: ASSERT() valid ReadFileInfo Flags for INLINE_DATA req

In the ReadFile() function, if "RecordingFlags" is INLINE_DATA, then we
cover the following values of "ReadFileInfo->Flags":

- READ_FILE_GET_FILESIZE
- READ_FILE_ALLOCATE_AND_READ
- READ_FILE_SEEK_AND_READ

We don't do anything (just proceed to the end of the function) if
"ReadFileInfo->Flags" is anything else.

In reality the above three values cover the domain of the
UDF_READ_FILE_FLAGS enum type fully, and "ReadFileInfo->Flags" is only
ever set internally to UdfDxe. Therefore any other flag value would be a
bug in UdfDxe.

ASSERT() specifically that "ReadFileInfo->Flags" has been set correctly,
so that the reader is not left wondering what happens if none of the enum
constants match.

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>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Paulo Alcantara <pcacjr@zytor.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>