[X86] Correct byte offsets and data types in a comment. NFC.
[X86] Correct byte offsets and data types in a comment. NFC.

This matches the types of the struct members defined in
lib/CodeGen/SjLjEHPrepare.cpp, and the definition of this struct in libgcc.

Differential Revision: https://reviews.llvm.org/D38248

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@314275 91177308-0d34-0410-b5e6-96231b3b80d8

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