Unify landing pad information adding routines (NFC)

Summary:
We have `llvm::addLandingPadInfo` and `MachineFunction::addLandingPad`,
both of which add landing pad information to populate `LandingPadInfo`
but are called from different locations, which was confusing. This patch
unifies them with one `MachineFunction::addLandingPad` function, which
now has functionlities of both functions.

Reviewers: rnk

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D52428

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343018 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed