feat(xilinx): add support to get chipid

Add support for PM API SYS to get the chip ID from the target.
The API calls the IPI command to read the Chip idcode and revision.

Change-Id: Id4d7d812cbf77c5e2fc7785b8afb379214f8dd19
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
diff --git a/plat/xilinx/common/include/pm_api_sys.h b/plat/xilinx/common/include/pm_api_sys.h
index baed43d..e8a9627 100644
--- a/plat/xilinx/common/include/pm_api_sys.h
+++ b/plat/xilinx/common/include/pm_api_sys.h
@@ -66,6 +66,7 @@
 enum pm_ret_status pm_register_notifier(uint32_t device_id, uint32_t event,
 					uint32_t wake, uint32_t enable,
 					uint32_t flag);
+enum pm_ret_status pm_get_chipid(uint32_t *value);
 
 /**
  * Assigning of argument values into array elements.