MIPS: remove unused prototype kgdb_config

Trivial fix that removes an orphaned prototype.
Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3701/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

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

@@ -93,8 +93,4 @@ extern void mips_pcibios_init(void);
 #define mips_pcibios_init() do { } while (0)
 #endif
 
-#ifdef CONFIG_KGDB
-extern void kgdb_config(void);
-#endif
-
 #endif  /* __ASM_MIPS_BOARDS_GENERIC_H */