Tegra194: SiP: Fix Rule 8.4 and Rule 10.4 violation

Rule 8.4, A compatible declaration shall be visible when an object
  or function with external linkage is defined.

Add function delaration to the header file.
Add suffix U to the unsigned constant define.

Change-Id: I54eba913a5fa38e4fdf3655931dc421d9510c691
Signed-off-by: Anthony Zhou <anzhou@nvidia.com>
diff --git a/plat/nvidia/tegra/soc/t194/plat_sip_calls.c b/plat/nvidia/tegra/soc/t194/plat_sip_calls.c
index 04602f0..03dad85 100644
--- a/plat/nvidia/tegra/soc/t194/plat_sip_calls.c
+++ b/plat/nvidia/tegra/soc/t194/plat_sip_calls.c
@@ -23,7 +23,7 @@
 /*******************************************************************************
  * Tegra186 SiP SMCs
  ******************************************************************************/
-#define TEGRA_SIP_ENABLE_FAKE_SYSTEM_SUSPEND		0xC2FFFE03
+#define TEGRA_SIP_ENABLE_FAKE_SYSTEM_SUSPEND		0xC2FFFE03U
 
 /*******************************************************************************
  * This function is responsible for handling all T186 SiP calls