KVM: arm64: Implement PV_SCHED_FEATURES call

virt inclusion
category: feature
bugzilla: 47624
CVE: NA

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This provides a mechanism for querying which paravirtualized sched
features are available in this hypervisor.

Add some SMCCC compatible hypercalls for PV sched features:
  PV_SCHED_FEATURES:       0xC5000090
  PV_SCHED_IPA_INIT:       0xC5000091
  PV_SCHED_IPA_RELEASE:    0xC5000092

Also add the header file which defines the ABI for the paravirtualized
sched features we're about to add.

Signed-off-by: Zengruan Ye <yezengruan@huawei.com>
Reviewed-by: Zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>