MdeModulePkg/UdfDxe: Add type cast to fix build failure in VS tools

MdeModulePkg/UdfDxe: Add type cast to fix build failure in VS tools

V3: Remove one unnecessay type cast in patch 1.
Codes:
if (FilePosition + ExtentLength > ReadFileInfo->FilePosition) {
  Offset = ReadFileInfo->FilePosition - FilePosition;
  if (Offset < 0) {
    Offset = -(Offset)
  }
...
}
Offset is UINT64 can not < 0, so the code logic may have some issue.
and Offset = -(Offset) may build failure in some circumstance.
Previously type cast Offset to INT64 to fix build break. Now remove
the type cast. Then can to check the code logic later.

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 1.0
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Paulo Alcantara <pcacjr@zytor.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>