agx: Zero r0l before first use of control flow

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11023>

src/asahi/compiler/agx_compiler.h

@@ -334,6 +334,9 @@ typedef struct {
    /* I don't really understand how writeout ops work yet */
    bool did_writeout;
 
+   /* Has r0l been zeroed yet due to control flow? */
+   bool any_cf;
+
    /* Number of nested control flow structures within the innermost loop. Since
     * NIR is just loop and if-else, this is the number of nested if-else
     * statements in the loop */