coresight: remove an unnecessary if statement which validates cpu id

CPU id returned by raw_smp_processor_id() is guaranteed to be less than
NR_CPUS. So etmdrvdata array will never do out of bound accesses. Remove an
unnecessary if statement which validates this.

Change-Id: I4a46f488ba8583cfbc5bc44c7679fb93a6f6b09b
Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>