ASoC: cx2072x: remove redundant assignment to pulse_len

Variable pulse_len is being initialized to 1 however this value is
never read and pulse_len is being re-assigned later in a switch
statement.  Clean up the code by removing the redundant initialization.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>