YH8xx,YH9xx: Keymap improvement

The main "innovation" in this patch are two "virtual buttons"
for the record switch on YH92x targets. When the switch state
changes, a single BUTTON_REC_SW_ON or .._OFF button event will
be generated. Thus keymap code can react on switching, but
not on the actual state of the switch.

Wherever sensible, the following user scheme is applied:
- use PLAY as confirm button
- use REW button or Long REW to exit
- use REC (YH820) or FFWD (YH92X) as modifier key for button combos

Change-Id: Ic8d1db9cc6869daed8dda98990dfdf7f6fd5d5a1

firmware/target/arm/samsung/button-target.h

@@ -39,9 +39,22 @@ void remote_int(void);
 #define BUTTON_PLAY         0x00000010
 #define BUTTON_REW          0x00000020
 #define BUTTON_FFWD         0x00000040
+#if defined(SAMSUNG_YH820) /* YH820 has record button */
 #define BUTTON_REC          0x00000080
+#else /* virtual buttons for record switch state change on YH92x */
+#define BUTTON_REC_SW_ON    0x00000080
+#define BUTTON_REC_SW_OFF   0x00000100
+/* TODO: most of the plugin keymaps rely on the REC button,
+   so I kept the following line to prevent compile errors.
+   This line has to be removed as soon as all plugin keymaps are fixed! */
+#define BUTTON_REC          0x00000200
+#endif
 
+#if defined(SAMSUNG_YH820)
 #define BUTTON_MAIN         0x000000ff
+#else
+#define BUTTON_MAIN         0x000001ff
+#endif
 
 #define BUTTON_RC_PLUS      BUTTON_UP
 #define BUTTON_RC_MINUS     BUTTON_DOWN