x86: Remove video_init() prototype from u-boot-x86.h

This function is not intended to be exported from the video drivers, so
remove the prototype. This fixes an error:

cfb_console.c:1793:12: error: static declaration of 'video_init' follows non-static declaration

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/include/asm/u-boot-x86.h

@@ -63,7 +63,6 @@ u32 isa_map_rom(u32 bus_addr, int size);
 
 /* arch/x86/lib/... */
 int video_bios_init(void);
-int video_init(void);
 
 void	board_init_f_r_trampoline(ulong) __attribute__ ((noreturn));
 void	board_init_f_r(void) __attribute__ ((noreturn));