ARM: OMAP2+: powerdomain: avoid testing whether an unsigned char is less than 0

_pwrdm_save_clkdm_state_and_activate() tried to test one of its
unsigned arguments to determine whether it was less than zero.  Fix by
moving the error test to the caller.
Reported-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>

arch/arm/mach-omap2/powerdomain.c

@@ -52,7 +52,6 @@ enum {
 #define ALREADYACTIVE_SWITCH		0
 #define FORCEWAKEUP_SWITCH		1
 #define LOWPOWERSTATE_SWITCH		2
-#define ERROR_SWITCH			3
 
 /* pwrdm_list contains all registered struct powerdomains */
 static LIST_HEAD(pwrdm_list);
@@ -233,10 +232,7 @@ static u8 _pwrdm_save_clkdm_state_and_activate(struct powerdomain *pwrdm,
 {
 	u8 sleep_switch;
 
-	if (curr_pwrst < 0) {
-		WARN_ON(1);
-		sleep_switch = ERROR_SWITCH;
-	} else if (curr_pwrst < PWRDM_POWER_ON) {
+	if (curr_pwrst < PWRDM_POWER_ON) {
 		if (curr_pwrst > pwrst &&
 		    pwrdm->flags & PWRDM_HAS_LOWPOWERSTATECHANGE &&
 		    arch_pwrdm->pwrdm_set_lowpwrstchange) {
@@ -1091,7 +1087,8 @@ int pwrdm_post_transition(struct powerdomain *pwrdm)
  */
 int omap_set_pwrdm_state(struct powerdomain *pwrdm, u8 pwrst)
 {
-	u8 curr_pwrst, next_pwrst, sleep_switch;
+	u8 next_pwrst, sleep_switch;
+	int curr_pwrst;
 	int ret = 0;
 	bool hwsup = false;
 
@@ -1107,16 +1104,17 @@ int omap_set_pwrdm_state(struct powerdomain *pwrdm, u8 pwrst)
 	pwrdm_lock(pwrdm);
 
 	curr_pwrst = pwrdm_read_pwrst(pwrdm);
+	if (curr_pwrst < 0) {
+		ret = -EINVAL;
+		goto osps_out;
+	}
+
 	next_pwrst = pwrdm_read_next_pwrst(pwrdm);
 	if (curr_pwrst == pwrst && next_pwrst == pwrst)
 		goto osps_out;
 
 	sleep_switch = _pwrdm_save_clkdm_state_and_activate(pwrdm, curr_pwrst,
 							    pwrst, &hwsup);
-	if (sleep_switch == ERROR_SWITCH) {
-		ret = -EINVAL;
-		goto osps_out;
-	}
 
 	ret = pwrdm_set_next_pwrst(pwrdm, pwrst);
 	if (ret)