There are a few places doing assignments in if condition in ALSA PCM
and OSS emulation layers, which is a bad coding style that may confuse
readers and occasionally lead to bugs.

This patch is merely for coding-style fixes, no functional changes.

Link: https://lore.kernel.org/r/20210608140540.17885-56-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>