docs/perf: Add ampere_cspmu to toctree to fix a build warning

Add ampere_cspmu to toctree in order to address the following warning
produced when building documents:

	Documentation/admin-guide/perf/ampere_cspmu.rst: WARNING: document isn't included in any toctree

Reported-by: Stephen Rothwell <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 53a810a ("perf: arm_cspmu: ampere_cspmu: Add support for Ampere SoC PMU")
Signed-off-by: Ilkka Koskinen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: ilkka-koskinen

Documentation/admin-guide/perf/index.rst

@@ -22,3 +22,4 @@ Performance monitor support
    nvidia-pmu
    meson-ddr-pmu
    cxl
+   ampere_cspmu