[NANO130] Fix CLK_Idle incorrectly enters into deep sleep mode

This can happen with CLK_PowerDown() called first and then CLK_Idle() called.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_NANO100/device/StdDriver/nano100_clk.c

@@ -70,7 +70,9 @@ void CLK_EnableCKO(uint32_t u32ClkSrc, uint32_t u32ClkDiv)
   */
 void CLK_PowerDown(void)
 {
-    SCB->SCR = SCB_SCR_SLEEPDEEP_Msk;
+    /* Set the processor uses deep sleep as its low power mode */
+    SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
+
     CLK->PWRCTL |= (CLK_PWRCTL_PD_EN_Msk | CLK_PWRCTL_WK_DLY_Msk );
     __WFI();
 }
@@ -81,6 +83,9 @@ void CLK_PowerDown(void)
   */
 void CLK_Idle(void)
 {
+    /* Set the processor uses sleep as its low power mode */
+    SCB->SCR &= ~SCB_SCR_SLEEPDEEP_Msk;
+
     CLK->PWRCTL &= ~(CLK_PWRCTL_PD_EN_Msk );
     __WFI();
 }