This patch adds a devres-supported helper for requesting an ISA DMA
channel that will be automatically freed at the device unbinding.
It'll be used by quite a few ISA sound drivers.

Link: https://lore.kernel.org/r/20210715075941.23332-4-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>