feat(zynqmp): resolve the misra 10.1 warnings

MISRA Violation: MISRA-C:2012 R.10.1
1) The expression of non-boolean essential type is being interpreted as a
boolean value for the operator.
2) The operand to the operator does not have an essentially unsigned type.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@xilinx.com>
Change-Id: I97bbc056f4fee167742429e144144ba793bf77b3
diff --git a/plat/xilinx/zynqmp/pm_service/pm_api_clock.c b/plat/xilinx/zynqmp/pm_service/pm_api_clock.c
index bfc6e44..c6bed7d 100644
--- a/plat/xilinx/zynqmp/pm_service/pm_api_clock.c
+++ b/plat/xilinx/zynqmp/pm_service/pm_api_clock.c
@@ -2610,7 +2610,7 @@
 		}
 	}
 
-	for (i = 0; i < 3; i++) {
+	for (i = 0; i < 3U; i++) {
 		parents[i] = clk_parents[index + i];
 		if (clk_parents[index + i] == CLK_NA_PARENT) {
 			break;