[IR] Use CallBase to simplify some code

Summary:
This patch does the following to simplify the asm-goto patch

-Move isInlineAsm from CallInst to CallBase to share with CallBrInst in the asm-goto patch.
-Forward CallSite's data_operands_begin()/data_operands_end() to CallBase's implementation.
-Forward CallSite's getOperandBundlesAsDefs to CallBase.

Reviewers: chandlerc

Reviewed By: chandlerc

Subscribers: nickdesaulniers, llvm-commits

Differential Revision: https://reviews.llvm.org/D57415

llvm-svn: 352600