docs: firmware: qcom_scm: Fix kernel-doc warning

docs: firmware: qcom_scm: Fix kernel-doc warning

Add description for members of qcom_scm_desc struct to avoid:

drivers/firmware/qcom/qcom_scm.h:56: warning: Function parameter or struct
member 'svc' not described in 'qcom_scm_desc'

drivers/firmware/qcom/qcom_scm.h:56: warning: Function parameter or struct
member 'cmd' not described in 'qcom_scm_desc'

drivers/firmware/qcom/qcom_scm.h:56: warning: Function parameter or struct
member 'owner' not described in 'qcom_scm_desc'

Signed-off-by: Unnathi Chalicheemala <unnathi.chalicheemala@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250403-fix_scm_doc_warn-v1-1-9cd36345db77@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>