Don't cast the return value of malloc/realloc

This patch has been generated by the following Coccinelle semantic
patch:

// Don't cast the return value of malloc/realloc.
//
// Casting the return value of malloc/realloc only stands to hide
// errors.

@@
type T;
expression E1, E2;
@@
- (T)
(
_mesa_align_calloc(E1, E2)
|
_mesa_align_malloc(E1, E2)
|
calloc(E1, E2)
|
malloc(E1)
|
realloc(E1, E2)
)

src/mesa/tnl/t_vb_program.c

@@ -521,7 +521,7 @@ init_vp(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
 
    /* a few other misc allocations */
    _mesa_vector4f_alloc( &store->ndcCoords, 0, size, 32 );
-   store->clipmask = (GLubyte *) _mesa_align_malloc(sizeof(GLubyte)*size, 32 );
+   store->clipmask = _mesa_align_malloc(sizeof(GLubyte)*size, 32 );
 
    return GL_TRUE;
 }