mxs: Clarify why we poweroff in case of brownout in 5v conflict

If VDDIO has a brownout, then the VDD5V_GT_VDDIO becomes unreliable
but this wasn't clear on code so a comment has been added to clarify
it.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>

arch/arm/cpu/arm926ejs/mxs/spl_power_init.c

@@ -577,6 +577,10 @@ void mxs_handle_5v_conflict(void)
 		tmp = readl(&power_regs->hw_power_sts);
 
 		if (tmp & POWER_STS_VDDIO_BO) {
+			/*
+			 * VDDIO has a brownout, then the VDD5V_GT_VDDIO becomes
+			 * unreliable
+			 */
 			mxs_powerdown();
 			break;
 		}