asoc: rt5639: fix missing regmap_exit during remove

asoc: rt5639: fix missing regmap_exit during remove

without regmap_exit in remove, next modprobe of
modprobe used to complain of
	"Failed to create debugfs directory"
due to stale debugfs directory.

Bug 200038898

Change-Id: I1579121748ebf14e216d9e29fbb607bda1de31f9
(cherry picked from commit Ie6373f40b50c1307ee7d114dc0f44164c4b426eb)
Reviewed-on: http://git-master/r/542646
Signed-off-by: Shreshtha SAHU <ssahu@nvidia.com>
Reviewed-on: http://git-master/r/554154
GVS: Gerrit_Virtual_Submit
Reviewed-by: Sumit Bhattacharya <sumitb@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>