ENGR00224912 mxc v4l2 capture:Correct mclk enable/disable

ENGR00224912 mxc v4l2 capture:Correct mclk enable/disable

1) Change to enable/disable mclk only in open, release,
suspend and resume functions, since we may simply think that
sensor or mclk will be used soon after cam->open_count is non-zero.
2) Fix a bug when calling ipu_csi_enable_mclk_if() with wrong
parameter(cam->csi should be cam->mclk_source) in mxc_v4l2_close()
and in mxc_v4l2_s_ctrl() with V4L2_CID_MXC_SWITCH_CAM control id.

Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
(cherry picked from commit be689b81ac24c0a4373a989664ec51ad77db0ced)