firmware: qcom_scm: Add dependent headers to qcom_scm.h

qcom_scm.h makes heavy use of <linux/types.h> and <linux/cpumask.h>.
Add the dependent header files so that users of SCM don't need to
include header files they don't otherwise use.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>