[PR/target 100316] Allow constant address for __builtin___clear_cache.

[PR/target 100316] Allow constant address for __builtin___clear_cache.

__builtin___clear_cache was able to accept constant address for the
argument, but it seems no longer accept recently, and it even not
accept constant address which is hold in variable when optimization is
enable:

```
void foo3(){
  void *yy = (void*)0x1000;
  __builtin___clear_cache(yy, yy);
}
```

So this patch make BEGIN and END accept VOIDmode, like cselib_lookup_mem did per
Jim Wilson's suggestion.

```
static cselib_val *
cselib_lookup_mem (rtx x, int create)
{
  ...
  addr_mode = GET_MODE (XEXP (x, 0));
  if (addr_mode == VOIDmode)
    addr_mode = Pmode;
```

Changes v2 -> v3:
- Use gcc_assert rather than error, maybe_emit_call_builtin___clear_cache is
internal use only, and we already checked the type in other place.

Changes v1 -> v2:
- Check is CONST_INT intead of cehck mode, no new testcase, since
  constant value with other type like CONST_DOUBLE will catched by
  front-end.
e.g.
Code:
```c
void foo(){
  __builtin___clear_cache(1.11, 0);
}
```
Error message:
```
clearcache-double.c: In function 'foo':
clearcache-double.c:2:27: error: incompatible type for argument 1 of '__builtin___clear_cache'
    2 |   __builtin___clear_cache(1.11, 0);
      |                           ^~~~
      |                           |
      |                           double
clearcache-double.c:2:27: note: expected 'void *' but argument is of type 'double'
```

gcc/ChangeLog:

	PR target/100316
	* builtins.c (maybe_emit_call_builtin___clear_cache): Allow
	CONST_INT for BEGIN and END, and use gcc_assert rather than
	error.

gcc/testsuite/ChangeLog:

	PR target/100316
	* gcc.c-torture/compile/pr100316.c: New.