sparc: Prevent stfsr from directly following floating-point instruction

On LEON, if the stfsr instruction is immediately following a floating-point
operation instruction in a running program, with no other instruction in
between the two, the stfsr might behave as if the order was reversed
between the two instructions and the stfsr occurred before the
floating-point operation.

Add a nop instruction before the stfsr to prevent this from happening.

Signed-off-by: Daniel Cederman <cederman@gaisler.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>