build: Drop check for sys/mman.h in favor of mmap() check

We already rely on just mmap() in other places.

configure

@@ -1578,7 +1578,6 @@ HEADERS_LIST="
     poll_h
     soundcard_h
     stdatomic_h
-    sys_mman_h
     sys_param_h
     sys_resource_h
     sys_select_h
@@ -4662,7 +4661,6 @@ check_header io.h
 check_header mach/mach_time.h
 check_header malloc.h
 check_header poll.h
-check_header sys/mman.h
 check_header sys/param.h
 check_header sys/resource.h
 check_header sys/select.h

libswscale/utils.c

@@ -27,7 +27,7 @@
 #include <math.h>
 #include <stdio.h>
 #include <string.h>
-#if HAVE_SYS_MMAN_H
+#if HAVE_MMAP
 #include <sys/mman.h>
 #if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
 #define MAP_ANONYMOUS MAP_ANON