Revert the LSDA change to scan_eh_tab.

This commit reverts the LSDA-related change in r211745.

The r211745 adds a new argument to scan_eh_tab(), i.e. lsda.
However, IMO, calling _Unwind_GetLanguageSpecificData() directly in
scan_eh_tab() was more intuitive and reduces several function call
to _Unwind_GetLanguageSpecificData() in __cxx_personality_v0().


git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@212037 91177308-0d34-0410-b5e6-96231b3b80d8