asoc: bolero: increase tx_mclk_users when enabling VA-MCLK

When enabling SVA, tx_mclk_users is not increased. If starting
and stopping recording after enabling SVA, tx_mclk will be closed
when powering down tx mclk widget. Increase tx_mclk_users when
enabling VA_MCLK to avoid mismatch.

Change-Id: I02d9400cf7309464bbba1e6749cfcfcf99f5876a
Signed-off-by: Meng Wang <mengw@codeaurora.org>