hw/arm: introduce xenpvh machine

Add a new machine xenpvh which creates a IOREQ server to register/connect with
Xen Hypervisor.

Optional: When CONFIG_TPM is enabled, it also creates a tpm-tis-device, adds a
TPM emulator and connects to swtpm running on host machine via chardev socket
and support TPM functionalities for a guest domain.

Extra command line for aarch64 xenpvh QEMU to connect to swtpm:
    -chardev socket,id=chrtpm,path=/tmp/myvtpm2/swtpm-sock \
    -tpmdev emulator,id=tpm0,chardev=chrtpm \
    -machine tpm-base-addr=0x0c000000 \

swtpm implements a TPM software emulator(TPM 1.2 & TPM 2) built on libtpms and
provides access to TPM functionality over socket, chardev and CUSE interface.
Github repo: https://github.com/stefanberger/swtpm
Example for starting swtpm on host machine:
    mkdir /tmp/vtpm2
    swtpm socket --tpmstate dir=/tmp/vtpm2 \
    --ctrl type=unixio,path=/tmp/vtpm2/swtpm-sock &

Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

include/hw/arm/xen_arch_hvm.h

@@ -0,0 +1,9 @@
+#ifndef HW_XEN_ARCH_ARM_HVM_H
+#define HW_XEN_ARCH_ARM_HVM_H
+
+#include <xen/hvm/ioreq.h>
+void arch_handle_ioreq(XenIOState *state, ioreq_t *req);
+void arch_xen_set_memory(XenIOState *state,
+                         MemoryRegionSection *section,
+                         bool add);
+#endif

include/hw/xen/arch_hvm.h

@@ -1,3 +1,5 @@
 #if defined(TARGET_I386) || defined(TARGET_X86_64)
 #include "hw/i386/xen_arch_hvm.h"
+#elif defined(TARGET_ARM) || defined(TARGET_ARM_64)
+#include "hw/arm/xen_arch_hvm.h"
 #endif