ALSA: asihpi: check pao in control_message()

ALSA: asihpi: check pao in control_message()

control_message() might be called with pao = NULL.
Here indicates control_message() as sample.

(B)	static void control_message(struct hpi_adapter_obj *pao, ...)
	{                                                   ^^^
		struct hpi_hw_obj *phw = pao->priv;
		...                      ^^^
	}

(A)	void _HPI_6205(struct hpi_adapter_obj *pao, ...)
	{                                      ^^^
		...
		case HPI_OBJ_CONTROL:
(B)			control_message(pao, phm, phr);
			break;          ^^^
		...
	}

	void HPI_6205(...)
	{
		...
(A)		_HPI_6205(NULL, phm, phr);
		...       ^^^^
	}

Therefore, We will get too many warning via cppcheck, like below

	sound/pci/asihpi/hpi6205.c:238:27: warning: Possible null pointer dereference: pao [nullPointer]
		 struct hpi_hw_obj *phw = pao->priv;
		                          ^
	sound/pci/asihpi/hpi6205.c:433:13: note: Calling function '_HPI_6205', 1st argument 'NULL' value is 0
		  _HPI_6205(NULL, phm, phr);
		            ^
	sound/pci/asihpi/hpi6205.c:401:20: note: Calling function 'control_message', 1st argument 'pao' value is 0
	   control_message(pao, phm, phr);
	                   ^
Set phr->error like many functions doing, and don't call _HPI_6205()
with NULL.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87ttypeaqz.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>