m68k: math-emu: Sanitize include guards

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

arch/m68k/math-emu/fp_arith.h

@@ -12,8 +12,8 @@
 
  */
 
-#ifndef FP_ARITH_H
-#define FP_ARITH_H
+#ifndef _FP_ARITH_H
+#define _FP_ARITH_H
 
 /* easy ones */
 struct fp_ext *
@@ -47,4 +47,4 @@ fp_fintrz(struct fp_ext *dest, struct fp_ext *src);
 struct fp_ext *
 fp_fscale(struct fp_ext *dest, struct fp_ext *src);
 
-#endif	/* FP_ARITH__H */
+#endif	/* _FP_ARITH_H */

arch/m68k/math-emu/fp_trig.h

@@ -15,8 +15,8 @@
 
 */
 
-#ifndef FP_TRIG_H
-#define FP_TRIG_H
+#ifndef _FP_TRIG_H
+#define _FP_TRIG_H
 
 #include "fp_emu.h"
 
@@ -29,4 +29,4 @@
    they return a status code, which should end up in %d0, if all goes
    well.  */
 
-#endif /* FP_TRIG__H */
+#endif /* _FP_TRIG_H */

arch/m68k/math-emu/multi_arith.h

@@ -15,8 +15,8 @@
    implement the subset of integer arithmetic that we need in order to
    multiply, divide, and normalize 128-bit unsigned mantissae.  */
 
-#ifndef MULTI_ARITH_H
-#define MULTI_ARITH_H
+#ifndef _MULTI_ARITH_H
+#define _MULTI_ARITH_H
 
 static inline void fp_denormalize(struct fp_ext *reg, unsigned int cnt)
 {
@@ -285,4 +285,4 @@ static inline void fp_putmant128(struct fp_ext *dest, union fp_mant128 *src,
 	}
 }
 
-#endif	/* MULTI_ARITH_H */
+#endif	/* _MULTI_ARITH_H */