BaseTools/VfrCompile: Remove the MAX_PATH limitation

BaseTools/VfrCompile: Remove the MAX_PATH limitation

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=579

Since we have already used LongFilePath() to convert
file path, so we can remove the MAX_PATH limitation.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Daniel Díaz <daniel.diaz@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>