Restore original code for __hexagon_subdf3

I was under the mistaken assumption I needed a `call` here but an
extended jump will suffice.  The call on its own would have failed
without an allocframe/dealloc.

Signed-off-by: Brian Cain <[email protected]>

Author: androm3da

lib/compiler_rt/hexagon.zig

@@ -814,9 +814,8 @@ fn __hexagon_subdf3() align(32) callconv(.naked) noreturn {
     asm volatile (
         \\ {
         \\   r3 = togglebit(r3,#31)
-        \\   call __hexagon_adddf3
+        \\   jump ##__hexagon_adddf3
         \\ }
-        \\ jumpr r31
     );
 }