CVE-2026-72280: KVM: arm64: nv: Drop bogus WARN for write to ZCR_EL2

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: nv: Drop bogus WARN for write to ZCREL2

It is entirely possible for a guest to write to the ZCREL2 sysreg alias while in a nested context, as it is expected if FEATNV2 is advertised to the L1 hypervisor.

Get rid of the bogus WARN which, since the hyp vectors were installed at this point, has the effect of a hyppanic...