msm:camera: Fix bug with registering fault handlers

Clients are not supposed to register more than the maximum fault
handlers supported. Hence add a check to reject additional
register calls if the maximum fault handler count is reached.

Change-Id: Idc3b908410bd82cb7452621f96a2a9883a50f5f1
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>