or1k: Only define fpu rouding and exceptions with hard-float

or1k: Only define fpu rouding and exceptions with hard-float

This test failure:

  math/test-fenv

If rounding mode and exception macros are defined then the fenv tests
run and always fail.  This patch adds an ifdef using the
__or1k_hard_float__ macro provided by gcc to avoid defining these fenv
macros when they cnnot be used.  This is similar to what is done in csky.

Note, I will post the or1k hard-float support soon. So, I prefer to
leave the hard-float bits here for now.