qcom-cpufreq: Use devm_kfree() to match devm_kzalloc()

Frequency table is allocated with devm_kzalloc() and thus should be
freed using devm_kfree().

Change-Id: I9c08838eadb9fc04bda9cc66596e1e0b45b3e4db
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>