KVM: SEV: Update KVM_AMD_SEV Kconfig entry and mention SEV-SNP

SEV-SNP support is present since commit 1dfe571c ("KVM: SEV: Add
initial SEV-SNP support") but Kconfig entry wasn't updated and still
mentions SEV and SEV-ES only. Add SEV-SNP there and, while on it, expand
'SEV' in the description as 'Encrypted VMs' is not what 'SEV' stands for.

No functional change.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240828122111.160273-1-vkuznets@redhat.comSigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/Kconfig

@@ -144,8 +144,10 @@ config KVM_AMD_SEV
 	select HAVE_KVM_ARCH_GMEM_PREPARE
 	select HAVE_KVM_ARCH_GMEM_INVALIDATE
 	help
-	  Provides support for launching Encrypted VMs (SEV) and Encrypted VMs
-	  with Encrypted State (SEV-ES) on AMD processors.
+	  Provides support for launching encrypted VMs which use Secure
+	  Encrypted Virtualization (SEV), Secure Encrypted Virtualization with
+	  Encrypted State (SEV-ES), and Secure Encrypted Virtualization with
+	  Secure Nested Paging (SEV-SNP) technologies on AMD processors.
 
 config KVM_SMM
 	bool "System Management Mode emulation"