Corrects typos and grammatical errors

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

lib/ed25519/add_scalar.c

@@ -45,7 +45,7 @@ void ed25519_add_scalar(unsigned char *public_key, unsigned char *private_key, c
         /* if we know the private key we don't need a point addition, which is faster */
         /* using a "timing attack" you could find out wether or not we know the private
            key, but this information seems rather useless - if this is important pass
-           public_key and private_key seperately in 2 function calls */
+           public_key and private_key separately in 2 function calls */
         if (private_key) {
             ge_scalarmult_base(&A, private_key);
         } else {

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;