ASoC: imx-wm8962: Let codec driver enable/disable its MCLK

WM8962 needs its MCLK when powerup in wm8962_resume(). Thus it's better
to control the MCLK in codec driver. Thus remove the clock enable in
machine driver accordingly.

While at it, get rid of imx_wm8962_remove function since it is now
empty.

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>