psci_common: Resolve GCC static analysis false positive

Previously commit 555ebb34db8f3424c1b394df2f10ecf9c1f70901 attmpted to fix this
GCC issue:

services/std_svc/psci/psci_common.c: In function 'psci_do_state_coordination':
services/std_svc/psci/psci_common.c:220:27: error: array subscript is above
array bounds [-Werror=array-bounds]
  psci_req_local_pwr_states[pwrlvl - 1][cpu_idx] = req_pwr_state;

This fix doesn't work as asserts aren't built in non-debug build flows.

Let's use GCCs #pragma option (documented here:
https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html

) to avoid
this false positive instead.
Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>

lib/psci/psci_common.c

@@ -194,8 +194,15 @@ static void psci_set_req_local_pwr_state(unsigned int pwrlvl,
 					 unsigned int cpu_idx,
 					 plat_local_state_t req_pwr_state)
 {
+	/*
+	 * This should never happen, we have this here to avoid
+	 * "array subscript is above array bounds" errors in GCC.
+	 */
 	assert(pwrlvl > PSCI_CPU_PWR_LVL);
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Warray-bounds"
 	psci_req_local_pwr_states[pwrlvl - 1][cpu_idx] = req_pwr_state;
+#pragma GCC diagnostic pop
 }
 
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