cxl: remove CONFIG_CXL_PMU entry in drivers/cxl/Kconfig

Commit 5d7107c727 ("perf: CXL Performance Monitoring Unit driver")
added the config entries for CXL_PMU in drivers/cxl/Kconfig and
drivers/perf/Kconfig, so it can be toggled from multiple locations:

[1] Device Drivers
     -> PCI support
       -> CXL (Compute Expres Link) Devices
         -> CXL Performance Monitoring Unit

[2] Device Drivers
     -> Performance monitor support
       -> CXL Performance Monitoring Unit

This complicates things, and nobody else does this.

I kept the one in drivers/perf/Kconfig because CONFIG_CXL_PMU controls
the compilation of drivers/perf/cxl_pmu.c.

Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

drivers/cxl/Kconfig

@@ -144,17 +144,4 @@ config CXL_REGION_INVALIDATION_TEST
 	  If unsure, or if this kernel is meant for production environments,
 	  say N.
 
-config CXL_PMU
-	tristate "CXL Performance Monitoring Unit"
-	default CXL_BUS
-	depends on PERF_EVENTS
-	help
-	  Support performance monitoring as defined in CXL rev 3.0
-	  section 13.2: Performance Monitoring. CXL components may have
-	  one or more CXL Performance Monitoring Units (CPMUs).
-
-	  Say 'y/m' to enable a driver that will attach to performance
-	  monitoring units and provide standard perf based interfaces.
-
-	  If unsure say 'm'.
 endif