mediatek: mt8192: Fix non-MISRA compliant code

CID 364146: Control flow issues (DEADCODE)

Since the value of PSTATE_PWR_LVL_MASK and the value the of PLAT_MAX_PWR_LVL
are equal on mt8192, the following equation never hold.

if (aff_lvl > PLAT_MAX_PWR_LVL) {
	return PSCI_E_INVALID_PARAMS;
}

Remove the deadcode to comply with MISRA standard.
Signed-off-by: Yidi Lin <yidi.lin@mediatek.com>
Change-Id: I71d0aa826eded8c3b5af961e733167ae40699398

plat/mediatek/mt8192/plat_pm.c

@@ -297,10 +297,6 @@ static int plat_validate_power_state(unsigned int power_state,
 	unsigned int aff_lvl = psci_get_pstate_pwrlvl(power_state);
 	unsigned int cpu = plat_my_core_pos();
 
-	if (aff_lvl > PLAT_MAX_PWR_LVL) {
-		return PSCI_E_INVALID_PARAMS;
-	}
-
 	if (pstate == PSTATE_TYPE_STANDBY) {
 		req_state->pwr_domain_state[0] = PLAT_MAX_RET_STATE;
 	} else {