KVM: arm64: Fix Trace Buffer trapping for protected VMs

KVM: arm64: Fix Trace Buffer trapping for protected VMs

For protected VMs in pKVM, the hypervisor should trap accesses to trace
buffer system registers if Trace Buffer isn't supported by the VM.
However, the current code only traps if Trace Buffer External Mode isn't
supported.

Fix this by checking for FEAT_TRBE (Trace Buffer) rather than
FEAT_TRBE_EXT.

Fixes: 9d5261269098 ("KVM: arm64: Trap external trace for protected VMs")
Reported-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20251211104710.151771-2-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>