firmware: qcom_scm-64: Fill SMC registers in qcom_scm_call_smccc

qcom_scm_call_smccc should be responsible for converting qcom_scm_desc
into arguments for smc call. Consolidate the dispersed logic to convert
qcom_scm_desc into smc arguments inside qcom_scm_call_smccc.

Change-Id: Ieae23c5fc6c77dbd76ef28dc4040b0f64de872c0
Signed-off-by: Elliot Berman <eberman@codeaurora.org>