[sw] Update source documentation

Fixes mostly spelling errors and outdated parameters.
Based on the warnings generated by Doxygen.

Signed-off-by: Tobias Wölfel <tobias.woelfel@mailbox.org>
diff --git a/sw/device/lib/flash_ctrl.h b/sw/device/lib/flash_ctrl.h
index 0ac86a4..33e3a95 100644
--- a/sw/device/lib/flash_ctrl.h
+++ b/sw/device/lib/flash_ctrl.h
@@ -99,7 +99,7 @@
 /**
  * Set flash controller default permissions.
  *
- * @param rd_end Read enable.
+ * @param rd_en Read enable.
  * @param prog_en Write enable.
  * @param erase_en Erase enable.
  */