nitro_enclaves: Add Kconfig for the Nitro Enclaves driver

Add kernel config entry for Nitro Enclaves, including dependencies.

Changelog

v9 -> v10

* Update commit message to include the changelog before the SoB tag(s).

v8 -> v9

* No changes.

v7 -> v8

* No changes.

v6 -> v7

* Remove, for now, the dependency on ARM64 arch. x86 is currently
supported, with Arm to come afterwards. The NE kernel driver can be
built for aarch64 arch.

v5 -> v6

* No changes.

v4 -> v5

* Add arch dependency for Arm / x86.

v3 -> v4

* Add PCI and SMP dependencies.

v2 -> v3

* Remove the GPL additional wording as SPDX-License-Identifier is
already in place.

v1 -> v2

* Update path to Kconfig to match the drivers/virt/nitro_enclaves
directory.
* Update help in Kconfig.

Reviewed-by: Alexander Graf <[e-mail]>
Signed-off-by: Andra Paraschiv <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/virt/Kconfig

···
 	     partition shuts down.
 
 source "drivers/virt/vboxguest/Kconfig"
+
+source "drivers/virt/nitro_enclaves/Kconfig"
 endif

drivers/virt/nitro_enclaves/Kconfig

···
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+
+# Amazon Nitro Enclaves (NE) support.
+# Nitro is a hypervisor that has been developed by Amazon.
+
+# TODO: Add dependency for ARM64 once NE is supported on Arm platforms. For now,
+# the NE kernel driver can be built for aarch64 arch.
+# depends on (ARM64 || X86) && HOTPLUG_CPU && PCI && SMP
+
+config NITRO_ENCLAVES
+	tristate "Nitro Enclaves Support"
+	depends on X86 && HOTPLUG_CPU && PCI && SMP
+	help
+	  This driver consists of support for enclave lifetime management
+	  for Nitro Enclaves (NE).
+
+	  To compile this driver as a module, choose M here.
+	  The module will be called nitro_enclaves.