decodetree: Suppress redundant declaration warnings

decodetree: Suppress redundant declaration warnings

We can tell that a decodetree input file is "secondary" when it
uses an argument set marked "!extern".  This indicates that at
least one of the insn translation functions will have already
been declared by the "primary" input file, but given only the
secondary we cannot tell which.

Avoid redundant declaration warnings by suppressing them with pragmas.

Tested-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Suggested-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>