agx: Add push_exec alias

Use the same canonical form as Metal, so the disassembler can alias it
back.

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

src/asahi/compiler/agx_builder.h.py

@@ -151,6 +151,12 @@ agx_fmov_to(agx_builder *b, agx_index dst0, agx_index src0)
    return agx_fadd_to(b, dst0, src0, agx_negzero());
 }
 
+static inline agx_instr *
+agx_push_exec(agx_builder *b, unsigned n)
+{
+   return agx_if_fcmp(b, agx_zero(), agx_zero(), n, AGX_FCOND_EQ, false);
+}
+
 #endif
 """