target-arm: Signal InvalidOp for Neon GE and GT compares of QNaN

If the input to a Neon float comparison is a quiet NaN, the ARM ARM
specifies that we should raise InvalidOp if the comparison is GE or GT
but not for EQ. (Signaling NaNs raise InvalidOp regardless). This means
only EQ should use the _quiet version of the comparison function.

We implement this by cleaning up the comparison helpers to call the
appopriate versions of the softfloat simple comparison functions
(float32_le and friends) rather than the generic float32_compare functions.
This makes them simple enough that they are clearer opencoded rather
than macroised.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
