JIT: remove "accurate fcmp" option

This doesn't seem to be necessary anymore now that FPRF is implemented in the
JIT. Technically, this isn't the same as before, since the JIT doesn't
implement the fcmp exception semantics, but as far as testing has shown, this
doesn't seem necessary.

This should make games that use FPRF a few percent faster (e.g. F-Zero GX)
since fcmpx no longer has to be fallbacked.