ACRN: Initialize the depriv_boot env to avoid the uninitialized RSDP

Currently when get_rsdp is called, the EFI depriv_boot env is not initialized.
In such case it will fail to get the ACPI table.
On the old platform it still can parse the ACPI table from legacy platform.
But it will fail on the new platform.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>

hypervisor/boot/guest/deprivilege_boot.c

@@ -60,6 +60,7 @@ static uint64_t get_depri_boot_ap_trampoline(void)
 
 static void* get_depri_boot_rsdp(void)
 {
+	init_depri_boot();
 	return hpa2hva((uint64_t)(depri_boot_ctx.rsdp));
 }