Tegra: enable 'signed-comparison' compilation warning/errors

This patch enables the 'sign-compare' flag, to enable warning/errors
for comparisons between signed/unsigned variables. The warning has
been enabled for all the Tegra platforms, to start with.

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
diff --git a/lib/psci/psci_main.c b/lib/psci/psci_main.c
index 2a6644b..257479a 100644
--- a/lib/psci/psci_main.c
+++ b/lib/psci/psci_main.c
@@ -209,7 +209,7 @@
 int psci_affinity_info(u_register_t target_affinity,
 		       unsigned int lowest_affinity_level)
 {
-	unsigned int target_idx;
+	int target_idx;
 
 	/* We dont support level higher than PSCI_CPU_PWR_LVL */
 	if (lowest_affinity_level > PSCI_CPU_PWR_LVL)