libm/math: Set errno to ERANGE for pow(0, -y)

POSIX says that the errno for pow(0, -y) should be ERANGE instead of
EDOM.

https://pubs.opengroup.org/onlinepubs/9699919799/functions/pow.html

Signed-off-by: Keith Packard <keithp@keithp.com>

newlib/libm/math/w_pow.c

@@ -84,8 +84,7 @@ PORTABILITY
 	    }
 	    if(finite(y)&&y<0.0) {
 		/* 0**neg */
-		errno = EDOM;
-		return -HUGE_VAL;
+		errno = ERANGE;
 	    }
 	    return z;
 	}

newlib/libm/math/wf_pow.c

@@ -50,8 +50,7 @@
 	    }
 	    if(finitef(y)&&y<0.0f) {
 		/* 0**neg */
-		errno = EDOM;
-		return -HUGE_VALF;
+		errno = ERANGE;
 	    }
 	    return z;
 	}