thermal: hisilicon: use dev_dbg when bind sensors

Current code use dev_err to output log if kernel cannot bind any one
sensor in initialization. This is a strictly checking to make sure all
four sensors have to be used for system.

After enable thermal power allocator, usually system only use one sensor
for multiple actors. This patch changes to use dev_dbg so that avoid
confusion in boot log, and remove duplicate printing log.

Signed-off-by: Leo Yan <leo.yan@linaro.org>