Per [1], legacy calling convention supports up to 5 arguments and 3
return values. Create one function to support this combination, and
remove the original "atomic1" and "atomic2" variants for 1 and 2
arguments. This more closely aligns scm_legacy implementation with
scm_smc implementation.

[1]: https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree/drivers/soc/qcom/scm.c?h=kernel.lnx.4.9.r28-rel#n1024

Tested-by: Brian Masney <masneyb@onstation.org> # arm32
Tested-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Elliot Berman <eberman@codeaurora.org>
Link: https://lore.kernel.org/r/1578431066-19600-14-git-send-email-eberman@codeaurora.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>