Tegra186: fix defects flagged by MISRA scan

Main fixes:

Remove unused type conversion

Fix invalid use of function pointer [Rule 1.3]

Fix variable essential type doesn't match [Rule 10.3]

Voided non c-library functions whose return types are not used
 [Rule 17.7]

Change-Id: I23994c9d4d6a240080933d848d2b03865acaa833
Signed-off-by: Anthony Zhou <anzhou@nvidia.com>
diff --git a/plat/nvidia/tegra/soc/t186/plat_smmu.c b/plat/nvidia/tegra/soc/t186/plat_smmu.c
index 19e065c..2751fcb 100644
--- a/plat/nvidia/tegra/soc/t186/plat_smmu.c
+++ b/plat/nvidia/tegra/soc/t186/plat_smmu.c
@@ -305,7 +305,7 @@
 smmu_regs_t *plat_get_smmu_ctx(void)
 {
 	/* index of _END_OF_TABLE_ */
-	tegra186_smmu_context[0].val = ARRAY_SIZE(tegra186_smmu_context) - 1;
+	tegra186_smmu_context[0].val = (uint32_t)(ARRAY_SIZE(tegra186_smmu_context)) - 1U;
 
 	return tegra186_smmu_context;
 }