Corrects typos and grammatical errors

Improves readability across documentation and inline comments by fixing common spelling mistakes and duplicate words.

lib/nrf52/include/ble_l2cap.h

@@ -286,7 +286,7 @@ typedef struct
 /**@brief L2CAP event structure. */
 typedef struct
 {
-  uint16_t conn_handle;                                     /**< Connection Handle on which the event occured. */
+  uint16_t conn_handle;                                     /**< Connection Handle on which the event occurred. */
   uint16_t local_cid;                                       /**< Local Channel ID of the L2CAP channel, or
                                                                  @ref BLE_L2CAP_CID_INVALID if not present. */
   union

lib/nrf52/include/nrf52/nrf_mbr.h

@@ -164,7 +164,7 @@ typedef struct
  */
 typedef struct
 {
-  uint32_t *bl_src;  /**< Pointer to the source of the bootloader to be be copied.*/
+  uint32_t *bl_src;  /**< Pointer to the source of the bootloader to be copied.*/
   uint32_t bl_len;   /**< Number of 32 bit words to copy for BootLoader. */
 } sd_mbr_command_copy_bl_t;