Backports commit 6c1f6f2733a7692793135ea5ce72b829add99a50 from qemu
Move all of the fp helpers out of helper.c into a new file. This is code movement only. Since helper.c has no copyright header, take the one from cpu.h for the new file. Backports commit 37356079fcdb34e13abbed8ea0c00ca880c31247 from qemu