fix(versal): evaluate condition for boolean

This corrects the MISRA violation C2012-11.9:
The macro NULL shall be the only permitted form of integer
null pointer constant.
The condition is compared with NULL to get boolean result.

Change-Id: I7c01825c5588207085d327b5b0c7ca2c896da2dc
Signed-off-by: Maheedhar Bollapalli <maheedharsai.bollapalli@amd.com>
diff --git a/plat/xilinx/versal/plat_psci.c b/plat/xilinx/versal/plat_psci.c
index 74c5bf3..a299d14 100644
--- a/plat/xilinx/versal/plat_psci.c
+++ b/plat/xilinx/versal/plat_psci.c
@@ -250,7 +250,7 @@
 
 	uint32_t pstate = psci_get_pstate_type(power_state);
 
-	assert(req_state);
+	assert(req_state != NULL);
 
 	/* Sanity check the requested state */
 	if (pstate == PSTATE_TYPE_STANDBY) {