ASoC: intel: bytcr_rt5651: add null check to support_button_press

When removing sof module the support_button_press function will oops
because hp_jack pointer is not checked for NULL. So add a check to fix
this.

Signed-off-by: Jaska Uimonen <jaska.uimonen@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190927201408.925-2-pierre-louis.bossart@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>