ASoC: WCD9304: Apply digital gain after digital path is turned ON

For the digital gain to be applied on the codec it is required to write
the digital gain register after the digital portion of the codec is
turned ON. This applies both for RX and TX digital path setup. Fix digital
gain setting sequence for RX and TX paths by rewriting the gain register
once the digital path is turned ON

Change-Id: I7b9c59c1b29b838845d27e406ba0f8a004c868b1
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>