LoongArch: Remove dead code in relocate_new_kernel

The initial aim is to silence the following objtool warning:

arch/loongarch/kernel/relocate_kernel.o: warning: objtool: relocate_new_kernel+0x74: unreachable instruction

There are two adjacent "b" instructions, the second one is unreachable,
it is dead code, just remove it.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Co-developed-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/relocate_kernel.S

@@ -72,7 +72,6 @@ copy_word:
 	LONG_ADDI	s5, s5, -1
 	beqz		s5, process_entry
 	b		copy_word
-	b		process_entry
 
 done:
 	ibar		0