KVM: arm: Add 32bit get/set events support

arm64's new use of KVMs get_events/set_events API calls isn't just
or RAS, it allows an SError that has been made pending by KVM as
part of its device emulation to be migrated.

Wire this up for 32bit too.

We only need to read/write the HCR_VA bit, and check that no esr has
been provided, as we don't yet support VDFSR.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Dongjiu Geng <gengdongjiu@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/virtual/kvm/api.txt

@@ -835,7 +835,7 @@ struct kvm_clock_data {
 
 Capability: KVM_CAP_VCPU_EVENTS
 Extended by: KVM_CAP_INTR_SHADOW
-Architectures: x86, arm64
+Architectures: x86, arm, arm64
 Type: vcpu ioctl
 Parameters: struct kvm_vcpu_event (out)
 Returns: 0 on success, -1 on error
@@ -883,7 +883,7 @@ Only two fields are defined in the flags field:
 - KVM_VCPUEVENT_VALID_SMM may be set in the flags field to signal that
   smi contains a valid state.
 
-ARM64:
+ARM/ARM64:
 
 If the guest accesses a device that is being emulated by the host kernel in
 such a way that a real device would generate a physical SError, KVM may make
@@ -934,7 +934,7 @@ struct kvm_vcpu_events {
 
 Capability: KVM_CAP_VCPU_EVENTS
 Extended by: KVM_CAP_INTR_SHADOW
-Architectures: x86, arm64
+Architectures: x86, arm, arm64
 Type: vcpu ioctl
 Parameters: struct kvm_vcpu_event (in)
 Returns: 0 on success, -1 on error
@@ -961,7 +961,7 @@ shall be written into the VCPU.
 
 KVM_VCPUEVENT_VALID_SMM can only be set if KVM_CAP_X86_SMM is available.
 
-ARM64:
+ARM/ARM64:
 
 Set the pending SError exception state for this VCPU. It is not possible to
 'cancel' an Serror that has been made pending.