firmware: qcom: scm: Add qcom_scm_set_warm_boot_addr function

A core can be powered down for cpuidle or when it is hotplugged off. In
either case, the warmboot return address would be different. Allow
setting the warmboot address for a specific cpu, optimize and write to
the firmware, if the address is different than the previously set
address.

Export qcom_scm_set_warm_boot_addr function move the warm boot flags to
implementation.

Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>