ARM: dts: qcom: msm8974: switch TCSR mutex to MMIO

The TCSR mutex bindings allow device to be described only with address
space (so it uses MMIO, not syscon regmap).  This seems reasonable, as
TCSR mutex is actually a dedicated IO address space, and it also fixes
DT schema checks:

  qcom-msm8974-sony-xperia-rhine-amami.dtb: tcsr-mutex: 'reg' is a required property
  qcom-msm8974-sony-xperia-rhine-amami.dtb: tcsr-mutex: 'syscon' does not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Luca Weiss <luca@z3ntu.xyz> # fairphone-fp2
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220920150414.637634-4-krzysztof.kozlowski@linaro.org