soc: qcom: rpmh-rsc: Clean code reading/writing TCS regs/cmds

soc: qcom: rpmh-rsc: Clean code reading/writing TCS regs/cmds

This patch makes two changes, both of which should be no-ops:

1. Make read_tcs_reg() / read_tcs_cmd() symmetric to write_tcs_reg() /
   write_tcs_cmd().

2. Change the order of operations in the above functions to make it
   more obvious to me what the math is doing.  Specifically first you
   want to find the right TCS, then the right register, and then
   multiply by the command ID if necessary.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Maulik Shah <mkshah@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Maulik Shah <mkshah@codeaurora.org>
Link: https://lore.kernel.org/r/20200413100321.v4.1.I1b754137e8089e46cf33fc2ea270734ec3847ec4@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>