aarch64.risu: add C3.6.22 Floating-point compare

this adds C3.6.22 including

FCMP (single precision, single precision zero)
FCMPE (single precision, single precision zero)

FCMP (double precision, double precision zero)
FCMPE (double precision, double precision zero)

Signed-off-by: Claudio Fontana <claudio.fontana@linaro.org>