msm: sps: Suppress bind/unbind attributes

SPS driver does not support manual bind/unbind operations
through sysfs. Suppress the bind/unbind nodes. Do not free
SPS struct in sps_device_de_init since it is being done in
sps_exit, and also to avoid use-after-free.

Change-Id: If6da6c5fb9d1a44d0420c6151f7f9d0a33cb2d04
Signed-off-by: Siva Kumar Akkireddi <sivaa@codeaurora.org>