Flash slides: stress that we are talking about "raw" flash

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>

slides/sysdev-flash-filesystems/sysdev-flash-filesystems.tex

@@ -1,7 +1,7 @@
 \section{Flash storage and filesystems}
 
 \begin{frame}
-  \frametitle{Block devices vs flash devices: reminder}
+  \frametitle{Block devices vs raw flash devices: reminder}
   \begin{itemize}
   \item Block devices:
     \begin{itemize}
@@ -12,7 +12,7 @@ \section{Flash storage and filesystems}
     \item Considered as reliable (if the storage media is not, some
       hardware or software parts are supposed to make it reliable)
     \end{itemize}
-  \item Flash devices:
+  \item Raw flash devices:
     \begin{itemize}
     \item Allow for random data access too
     \item Require special care before writing on the media (erasing