C200: Also flip the function of the volume buttons when display flip is enabled. I think it is more consistent, especially when thinking of cases where these buttons are used for something else (e.g. left/right in brickmania). Taken from FS#8393 by Volker Mische - add him to CREDITS too.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@18404 a1c6a512-1295-4272-9138-f99709370657

docs/CREDITS

@@ -415,6 +415,7 @@ Jelle Geerts
 Tadeusz Pyś
 Rostislav Chekan
 Florin Popescu
+Volker Mische
 
 The libmad team
 The wavpack team

firmware/drivers/button.c

@@ -437,6 +437,9 @@ static int button_flip(int button)
 #endif
 #if CONFIG_KEYPAD == RECORDER_PAD
         | BUTTON_F1 | BUTTON_F3
+#endif
+#if CONFIG_KEYPAD == SANSA_C200_PAD
+        | BUTTON_VOL_UP | BUTTON_VOL_DOWN
 #endif
         );
 
@@ -462,6 +465,12 @@ static int button_flip(int button)
     if (button & BUTTON_F3)
         newbutton |= BUTTON_F1;
 #endif
+#if CONFIG_KEYPAD == SANSA_C200_PAD
+    if (button & BUTTON_VOL_UP)
+        newbutton |= BUTTON_VOL_DOWN;
+    if (button & BUTTON_VOL_DOWN)
+        newbutton |= BUTTON_VOL_UP;
+#endif
 
     return newbutton;
 }