[Attributor] Deduce "align" attribute

Summary:
Deduce "align" attribute in attributor.

Reviewers: jdoerfert, sstefan1

Reviewed By: jdoerfert

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64152

llvm-svn: 367187