egl: fix in expected type

Function mincore expects a pointer of type char* but we use an unsigned
char* instead generating signedness related warnings.

v2: Made the fix FreeBSD specific because the type is unsigned char* for
Linux and char* for FreeBSD. (Adam Jackson)

v3: We'd rather cast the param to (void*) to avoid warnings in all
systems (Adam Jackson)

Signed-off-by: Eleni Maria Stea <elene.mst@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11298>

src/egl/main/eglglobals.c

@@ -147,7 +147,10 @@ _eglPointerIsDereferencable(void *p)
    /* align addr to page_size */
    addr &= ~(page_size - 1);
 
-   if (mincore((void *) addr, page_size, &valid) < 0) {
+   /* mincore expects &valid to be unsigned char* on Linux but char* on BSD:
+    * we cast pointers to void, to fix type mismatch warnings in all systems
+    */
+   if (mincore((void *) addr, page_size, (void*)&valid) < 0) {
       return EGL_FALSE;
    }