ASoC: Intel: Skylake: Fix potential NULL pointer dereference

Pointer 'mconfig' returned from call to skl_tplg_fe_get_cpr_module() can
be NULL. So check for the valid pointer before dereferencing.

Signed-off-by: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Signed-off-by: Guneshwor Singh <guneshwor.o.singh@intel.com>
Acked-By: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>