ALSA: ali5451: remove redundant variable capture_flag

Variable capture_flag is only ever assigned values, it is never read
and hence it is redundant. Remove it.

Addresses-Coverity ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20200208223443.38047-1-colin.king@canonical.com


Signed-off-by: Takashi Iwai <tiwai@suse.de>