aarch64.risu: add load/store excl insns for 32/64bit data
aarch64.risu: add load/store excl insns for 32/64bit data

add STXR, STLXR, STLR, LDXR, LDAXR, LDAR for 32bit and 64bit.

Signed-off-by: Claudio Fontana <5fe97b97070bc75ff3c7a6b130e2dcc62cbb9b58@linaro.org>

vivier/risu,stsquad/risu,stsquad/risu,stsquad/risu,vivier/risu