hvc_dcc: Disable preemption when cheking for smp_processor_id

smp_processor_id() complains if called from a preemptible
context. Hence, disable the preemption just before calling
this and enable it back later.

Change-Id: I6721796d11186eb15021b37d5ea8250afa0edda0
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>