sparc64: uprobes: add missing break

sparc64: uprobes: add missing break

Missing fallthrough causes failure with newer compilers:

arch/sparc/kernel/uprobes.c:284:2: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
  284 |         default:
      |         ^
arch/sparc/kernel/uprobes.c:284:2: note: insert 'break;' to avoid fall-through
  284 |         default:
      |         ^
      |         break;

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Andreas Larsson <andreas@gaisler.com>