ARM: OMAP: Remove remaining board-*.h includes from hardware.h

Also remove board-omap3beagle.h that is not included anywhere,
and move protoype for voiceblue_reset() from board-voiceblue.h
to system.h.

After this patch there are still board-ams-delta.h, board-sx1.h
and board-voiceblue.h that export some functions. These could
be removed if the functions were moved under drivers.

Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/include/mach/system.h

@@ -11,6 +11,8 @@
 
 #ifndef CONFIG_MACH_VOICEBLUE
 #define voiceblue_reset()		do {} while (0)
+#else
+extern void voiceblue_reset(void);
 #endif
 
 extern void omap_prcm_arch_reset(char mode);