MIPS: remove dead code from asm/u-boot-mips.h

Those wrappers for linker symbols were once used in the MIPS
specific board.c implementation. Since the migration to generic
board.c, those wrappers are dead code and can be removed.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

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

 /*
  * SPDX-License-Identifier:	GPL-2.0+
- *
- * Copyright (C) 2003 Wolfgang Denk, DENX Software Engineering, wd@denx.de
  */
 
-static inline unsigned long bss_start(void)
-{
-	extern char __bss_start[];
-	return (unsigned long) &__bss_start;
-}
+#ifndef _U_BOOT_MIPS_H_
+#define _U_BOOT_MIPS_H_
 
-static inline unsigned long bss_end(void)
-{
-	extern ulong __bss_end;
-	return (unsigned long) &__bss_end;
-}
-
-static inline unsigned long image_copy_end(void)
-{
-	extern char __image_copy_end[];
-	return (unsigned long) &__image_copy_end;
-}
+#endif /* _U_BOOT_MIPS_H_ */