Fix the return type of felem_is_zero_int which should be int.

Change argument type of xxxelem_is_zero_int to const void*
to avoid the need of type casts.

Fixes #4413
Reviewed-by: NAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4450)

crypto/ec/ecp_nistp224.c

@@ -700,7 +700,7 @@ static limb felem_is_zero(const felem in)
     return (zero | two224m96p1 | two225m97p2);
 }
 
-static limb felem_is_zero_int(const felem in)
+static int felem_is_zero_int(const void *in)
 {
     return (int)(felem_is_zero(in) & ((limb) 1));
 }
@@ -1366,7 +1366,6 @@ static void make_points_affine(size_t num, felem points[ /* num */ ][3],
                                              sizeof(felem),
                                              tmp_felems,
                                              (void (*)(void *))felem_one,
-                                             (int (*)(const void *))
                                              felem_is_zero_int,
                                              (void (*)(void *, const void *))
                                              felem_assign,

crypto/ec/ecp_nistp256.c

@@ -979,7 +979,7 @@ static limb smallfelem_is_zero(const smallfelem small)
     return result;
 }
 
-static int smallfelem_is_zero_int(const smallfelem small)
+static int smallfelem_is_zero_int(const void *small)
 {
     return (int)(smallfelem_is_zero(small) & ((limb) 1));
 }
@@ -1984,7 +1984,6 @@ static void make_points_affine(size_t num, smallfelem points[][3],
                                              sizeof(smallfelem),
                                              tmp_smallfelems,
                                              (void (*)(void *))smallfelem_one,
-                                             (int (*)(const void *))
                                              smallfelem_is_zero_int,
                                              (void (*)(void *, const void *))
                                              smallfelem_assign,

crypto/ec/ecp_nistp521.c

@@ -886,7 +886,7 @@ static limb felem_is_zero(const felem in)
     return is_zero;
 }
 
-static int felem_is_zero_int(const felem in)
+static int felem_is_zero_int(const void *in)
 {
     return (int)(felem_is_zero(in) & ((limb) 1));
 }
@@ -1806,7 +1806,6 @@ static void make_points_affine(size_t num, felem points[][3],
                                              sizeof(felem),
                                              tmp_felems,
                                              (void (*)(void *))felem_one,
-                                             (int (*)(const void *))
                                              felem_is_zero_int,
                                              (void (*)(void *, const void *))
                                              felem_assign,