soc: qcom: cpu: Allow CPU0 hotplug by fixing cold_boot_done flag

The cold_boot_done flag is maintained per cpu to ensure that the
cold boot sequence is done exactly once for every cpu. The CPU0
needs to set this flag explicitly since none of the cpu ops APIs are
executed for CPU0.

Change-Id: I2beab4f9847c29af9a592cb102f255a056b878d5
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>