ASoC: Intel: Skylake: Remove driver debugfs exit

For driver debugfs, debugfs_remove_recursive() is called which is not
needed as it is already done in ASoC core debugfs. And a device managed
memory need not be freed explicitly as device core frees it up. So
remove unnecessary skl_debugfs_exit().

Fixes: 5cdf6c09

 ASoC: ("Intel: Skylake: Add debugfs support")
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Guneshwor Singh <guneshwor.o.singh@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>