x86/kvm/Kconfig: Have KVM_AMD_SEV select ARCH_HAS_CC_PLATFORM

The functionality to load SEV-SNP guests by the host will soon rely on
cc_platform* helpers because the cpu_feature* API with the early
patching is insufficient when SNP support needs to be disabled late.

Therefore, pull that functionality in.

Fixes: 216d106c ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Link: https://lore.kernel.org/r/20240327154317.29909-4-bp@alien8.de

arch/x86/kvm/Kconfig

@@ -122,6 +122,7 @@ config KVM_AMD_SEV
 	default y
 	depends on KVM_AMD && X86_64
 	depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
+	select ARCH_HAS_CC_PLATFORM
 	help
 	  Provides support for launching Encrypted VMs (SEV) and Encrypted VMs
 	  with Encrypted State (SEV-ES) on AMD processors.