SEB and SEH instructions are not available on MIPS32R1. This caused several failures on
MIPS32R1 in mjsunit/wasm/* and mjsunit/asm test suites.
This fix simulates these instruction in MacroAssembler for those architectures that do not support them.

TEST=mjsunit/asm/sqlite3/sqlite-pointer-masking,mjsunit/wasm/embenchen/lua_binarytrees
BUG=

Review-Url: https://chromiumcodereview.appspot.com/2434973002
Cr-Commit-Position: refs/heads/master@{#40467}