mesa: Removed unnecessary check for NULL pointer when freeing memory

Note that it is OK to pass NULL pointers to this function since this commit:

mesa: modified _mesa_align_free() to accept NULL pointer
http://cgit.freedesktop.org/mesa/mesa/commit/?id=f0cc59d68a9f5231e8e2111393a1834858820735

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/main/bufferobj.c

@@ -562,8 +562,7 @@ _mesa_buffer_data( struct gl_context *ctx, GLenum target, GLsizeiptrARB size,
 
    (void) target;
 
-   if (bufObj->Data)
-      _mesa_align_free( bufObj->Data );
+   _mesa_align_free( bufObj->Data );
 
    new_data = _mesa_align_malloc( size, ctx->Const.MinMapBufferAlignment );
    if (new_data) {