chore(xilinx): follow kernel doc format for functional documentation

For TF-A, there is no format specified for functional documentation.
For AMD-Xilinx platforms, following kernel-doc format for the functional
documentation to make sure AMD-xilinx documentation is align with
actual code.

For example use kernel-doc from linux to call:
<linux>/scripts/kernel-doc -man -v 1 >/dev/null file...

Signed-off-by: Prasad Kummari <prasad.kummari@amd.com>
Change-Id: Idcc9def408b6c8da35b36f67ef82fc00890e998c
diff --git a/plat/xilinx/common/include/pm_api_sys.h b/plat/xilinx/common/include/pm_api_sys.h
index e8a9627..3fcb62f 100644
--- a/plat/xilinx/common/include/pm_api_sys.h
+++ b/plat/xilinx/common/include/pm_api_sys.h
@@ -68,7 +68,7 @@
 					uint32_t flag);
 enum pm_ret_status pm_get_chipid(uint32_t *value);
 
-/**
+/*
  * Assigning of argument values into array elements.
  */
 #define PM_PACK_PAYLOAD1(pl, mid, flag, arg0) {	\