cpu/cc2538: adapt and cleanup periph/hwrng

    Some minor adaptions due to cleanup in periph/adc and usage of
    vendor header files.

cpu/cc2538/periph/hwrng.c

@@ -21,22 +21,31 @@
  * @}
  */
 
+#include "vendor/hw_memmap.h"
+#include "vendor/hw_soc_adc.h"
+
 #include "cpu.h"
 #include "periph/hwrng.h"
 
+#define ENABLE_DEBUG (0)
+#include "debug.h"
+
+static cc2538_soc_adc_t *soc_adc = (cc2538_soc_adc_t *)SOC_ADC_BASE;
+
 void hwrng_init(void)
 {
     uint16_t seed = 0;
     int i;
 
     /* Make sure the RNG is on */
-    SOC_ADC->cc2538_adc_adccon1.ADCCON1bits.RCTRL = 0;
+    uint32_t reg32 = soc_adc->ADCCON1 & ~(SOC_ADC_ADCCON1_RCTRL_M);
+    soc_adc->ADCCON1 = reg32;
 
     /* Enable clock for the RF Core */
     SYS_CTRL_RCGCRFC = 1;
 
     /* Wait for the clock ungating to take effect */
-    while (SYS_CTRL_RCGCRFC != 1);
+    while (SYS_CTRL_RCGCRFC != 1) {}
 
     /* Infinite RX - FRMCTRL0[3:2] = 10. This will mess with radio operation */
     RFCORE_XREG_FRMCTRL0 = 0x00000008;
@@ -63,8 +72,8 @@ void hwrng_init(void)
     }
 
     /* Seed the high byte first: */
-    SOC_ADC_RNDL = (seed >> 8) & 0xff;
-    SOC_ADC_RNDL = seed & 0xff;
+    soc_adc->RNDH = (seed >> 8) & 0xff;
+    soc_adc->RNDL = seed & 0xff;
 
     /* Turn RF off: */
     RFCORE_SFR_RFST = ISRFOFF;
@@ -72,16 +81,16 @@ void hwrng_init(void)
 
 void hwrng_read(void *buf, unsigned int num)
 {
-    unsigned count;
     uint8_t *b = (uint8_t *)buf;
 
-    for (count = 0; count < num; ) {
+    for (unsigned count = 0; count < num; count++) {
         /* Clock the RNG LSFR once: */
-        SOC_ADC->cc2538_adc_adccon1.ADCCON1bits.RCTRL = 1;
-
+        soc_adc->ADCCON1 = soc_adc->ADCCON1 | (1UL << SOC_ADC_ADCCON1_RCTRL_S);
         /* Read up to 2 bytes of hwrng data: */
-        b[count++] = SOC_ADC_RNDL;
-        if (count >= num) break;
-        b[count++] = SOC_ADC_RNDH;
+        b[count] = soc_adc->RNDL;
+        count++;
+        if (count < num) {
+            b[count] = soc_adc->RNDH;
+        }
     }
 }