MIPS: Remove unused mips_display/_scroll_message() declarations

The mips_display/_scroll_message() have been removed since
commit 0b003749 ("MIPS: malta: Use img-ascii-lcd driver for LCD
display"), so remove them.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/mips-boards/generic.h

@@ -73,7 +73,4 @@ extern void mips_pcibios_init(void);
 #define mips_pcibios_init() do { } while (0)
 #endif
 
-extern void mips_scroll_message(void);
-extern void mips_display_message(const char *str);
-
 #endif	/* __ASM_MIPS_BOARDS_GENERIC_H */