KVM: arm64: Unconditionally include generic KVM's Kconfig

Unconditionally "source" the generic KVM Kconfig instead of wrapping it
with KVM=y.  A future patch will select HAVE_KVM so that referencing
HAVE_KVM in common kernel code doesn't break, and because KVM=y and
HAVE_KVM=n is weird.  Source the generic KVM Kconfig unconditionally so
that HAVE_KVM and KVM don't end up with a circular dependency.

Note, all but one of generic KVM's "configs" are of the HAVE_XYZ nature,
and the one outlier correctly takes a dependency on CONFIG_KVM, i.e. the
generic Kconfig is intended to be included unconditionally.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
[maz: made NVHE_EL2_DEBUG depend on KVM]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210921222231.518092-2-seanjc@google.com