sh: fpu: Add missing forward declarations

sh: fpu: Add missing forward declarations

arch/sh/kernel/cpu/sh4/fpu.c:389:6: warning: no previous prototype for ‘float_raise’ [-Wmissing-prototypes]
arch/sh/kernel/cpu/sh4/fpu.c:394:5: warning: no previous prototype for ‘float_rounding_mode’ [-Wmissing-prototypes]

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/1847145fc2181313b78bea8a81e6f0269d765968.1709326528.git.geert+renesas@glider.be
Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>