[PORT FROM R2] intel_mid_hsi: Cleaned-up reset sequence for avoiding RX errors.

[PORT FROM R2] intel_mid_hsi: Cleaned-up reset sequence for avoiding RX errors.

BZ: 15516

This patch is cleaning up the reset sequence of Intel HSI controller by:
- disabling the tasklet prior to resetting the hardware to prevent those
  tasklets to run after the transfer contexts have been freed thus protecting
  against a potential kernel panic;
- not disabling the IP clock generation and PLL, as this causes RX errors when
  the device is re-enabled without going into suspend mode. This error is not
  happening when the device is going through a suspend / resume cycle as it is
  un-powered and restarts in a safe state.

Change-Id: I404feb0c96840e9eeec4e78336b42a1254c4acff
Orig-Change-Id: I092434a4dfeb5dd2c6a31bc887e9115eff23fba4
Signed-off-by: Olivier Stoltz Douchet <olivierx.stoltz-douchet@intel.com>
Reviewed-on: http://android.intel.com:8080/31423
Reviewed-by: Robert, Denis <denis.robert@intel.com>
Reviewed-by: Akue, LoicX <loicx.akue@intel.com>
Reviewed-by: Pillet, VincentX <vincentx.pillet@intel.com>
Reviewed-by: Predon, Frederic <frederic.predon@intel.com>
Reviewed-by: Lebsir, SamiX <samix.lebsir@intel.com>
Tested-by: Lebsir, SamiX <samix.lebsir@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>