ASoC: wcd9xxx: restrict debugfs permission

Remove read permission for debugfs reg dump node
for group and users to not allow reading of wcd9xxx
registers.

CRs-fixed: 2113240
Change-Id: I73a22e140446828e694fdc95fde7ac4e051c9548
Signed-off-by: Karthikeyan Mani <kmani@codeaurora.org>