fix(pmu): check pmu is supported before using any of it

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: Ic0da2ed49c38d9b2d81c740ca9c3eedf1f562e57
diff --git a/tftf/tests/extensions/pmuv3/test_pmuv3.c b/tftf/tests/extensions/pmuv3/test_pmuv3.c
index 6d70548..725b4e7 100644
--- a/tftf/tests/extensions/pmuv3/test_pmuv3.c
+++ b/tftf/tests/extensions/pmuv3/test_pmuv3.c
@@ -201,10 +201,12 @@
 	u_register_t ctr_end[MAX_COUNTERS] = {0};
 	u_register_t ctr_cfg_end[MAX_COUNTERS] = {0};
 	u_register_t pmu_cfg_end[4];
-	int impl_ev_ctrs = (read_pmcr_el0() >> PMCR_EL0_N_SHIFT) & PMCR_EL0_N_MASK;
+	int impl_ev_ctrs;
 
 	SKIP_TEST_IF_PMUV3_NOT_SUPPORTED();
 
+	impl_ev_ctrs = (read_pmcr_el0() >> PMCR_EL0_N_SHIFT) & PMCR_EL0_N_MASK;
+
 	/* start from 0 so we know we can't overflow */
 	clear_counters();
 	/* pretend counters have just been used */