x86: Remove calculate_relocation_address()

Now that we have generic routine to calculate relocation address,
remove the x86 specific one which is now only used by coreboot.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/include/asm/init_helpers.h

@@ -8,8 +8,6 @@
 #ifndef _INIT_HELPERS_H_
 #define _INIT_HELPERS_H_
 
-int calculate_relocation_address(void);
-
 int init_cache_f_r(void);
 int init_bd_struct_r(void);
 int init_func_spi(void);