soc: qcom: hab: Updating return value for function attributed to kobject

Updating the return value of vchan_store, ctx_store, expimp_show
functions to return an integer count.

Submit code on behalf of Yashovardhan Bhatt.

Change-Id: I5c1ec7ed7add2471ed5809a9bb359d0b02792486
Signed-off-by: Zelong Ren <zeloren@codeaurora.org>