aoc/alsa: Remove call to irqs_disabled()

Since this isn't used anymore, remove it. It's causing a Werror failure
due to setting an unused variable.

Fixes: 2742a8c6 ("aoc/alsa: change pcm callbacks to be nonatomic")
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: Ia8385f13ca533f7312fe708339b6bc7a02a881b2