cxl/Kconfig: Default drivers to CONFIG_CXL_BUS

CONFIG_CXL_BUS is default 'n' as expected for new functionality. When
that is enabled do not make the end user hunt for all the expected
sub-options to enable. For example CONFIG_CXL_BUS without CONFIG_CXL_MEM
is an odd/expert configuration, so is CONFIG_CXL_MEM without
CONFIG_CXL_ACPI (on ACPI capable platforms). Default CONFIG_CXL_MEM and
CONFIG_CXL_ACPI to CONFIG_CXL_BUS.

Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162325450105.2293126.17046356425194082921.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/Kconfig

@@ -15,6 +15,7 @@ if CXL_BUS
 
 config CXL_MEM
 	tristate "CXL.mem: Memory Devices"
+	default CXL_BUS
 	help
 	  The CXL.mem protocol allows a device to act as a provider of
 	  "System RAM" and/or "Persistent Memory" that is fully coherent
@@ -49,6 +50,7 @@ config CXL_MEM_RAW_COMMANDS
 config CXL_ACPI
 	tristate "CXL ACPI: Platform Support"
 	depends on ACPI
+	default CXL_BUS
 	help
 	  Enable support for host managed device memory (HDM) resources
 	  published by a platform's ACPI CXL memory layout description.  See