[WebAssembly] Remove unused memory instructions and patterns

Summary:
Removes duplicated SIMD loads and store instructions and removes
patterns involving GlobalAddresses that were not used in any tests.

Reviewers: aheejin, sunfish

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67783

llvm-svn: 372648