[X86][ELF] Fix PR20243 - leaf frame pointer bug with TLS access

The ISel lowering for global TLS access in PIC mode was creating a pseudo 
instruction that is later expanded to a call, but the code was not 
setting the hasCalls flag in the MachineFrameInfo alongside the adjustsStack 
flag. This caused some functions to be mistakenly recognized as leaf functions,
and this in turn affected the decision to eliminate the frame pointer.

With the fix, hasCalls is properly set and the leaf frame pointer is correctly
preserved.

llvm-svn: 221695