Some include guards start with an underscore, others don't.
Some comments do not match the actual include guard.

Make them uniform, adhering to the "FP_<FOO>_H" format.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/8c84c8bf06c0c1e463c47f071891e2e83d5abdd2.1692283195.git.geert@linux-m68k.org