ALSA: sb: Don't allow changing the DMA mode during operations

[ Upstream commit ed29e073 ]

When a PCM stream is already running, one shouldn't change the DMA
mode via kcontrol, which may screw up the hardware.  Return -EBUSY
instead.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=218185
Link: https://patch.msgid.link/20250610064322.26787-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>