drivers: nrf24l01p: rename DELAY microsecond defines to *_US

drivers/nrf24l01p/include/nrf24l01p_settings.h

@@ -33,10 +33,10 @@ extern "C" {
 
 #define DELAY_CS_TOGGLE_TICKS       2
 #define DELAY_AFTER_FUNC_TICKS      2
-#define DELAY_CE_HIGH               (20)
-#define DELAY_CHANGE_PWR_MODE       (1500)
-#define DELAY_CHANGE_TXRX           (130)
-#define DELAY_CE_START              (5)
+#define DELAY_CE_HIGH_US            (20)
+#define DELAY_CHANGE_PWR_MODE_US    (1500)
+#define DELAY_CHANGE_TXRX_US        (130)
+#define DELAY_CE_START_US           (5)
 /*
  * This is the time which is needed to physically transmit the data.
  * Compare nrf24l01+ pruduct specification p.42. It is computed just