target-ppc: remove old CONFIG_SOFTFLOAT #ifdef

target-ppc has been switched to softfloat only long ago, but a
few #ifdef CONFIG_SOFTFLOAT have been forgotten. Remove them.

Cc: Alexander Graf <agraf@suse.de>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>