msm: cpufreq: Avoid NULL clock pointer references

The MSM CPUfreq driver defines a mapping from cpu number to clock
pointer. On SOCs with synchronous cpus, only the mapping for cpu#0
is defined, even though there may be more than 1 cpu. Handle this
case by skipping certain unnecessary initialization steps for SOCs
with synchronous cpus.

Change-Id: Iaeba7a8615e3cb7da2c725250db92595450bfa46
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>