LoongArch: Align the address of kernel_entry to 4KB

Align the address of kernel_entry to 4KB, to avoid early tlb miss
exception in case the entry code crosses page boundary.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/head.S

@@ -14,6 +14,8 @@
 
 	__REF
 
+	.align 12
+
 SYM_CODE_START(kernel_entry)			# kernel entry point
 
 	/* Config direct window and set PG */