Move kernel related files into kernel

Makefile

@@ -10,7 +10,7 @@ OBJDUMP = $(TOOLPREFIX)-objdump
 
 ASFLAGS = -march=rv64gc -mabi=lp64
 
-LDFLAGS = -Tkernel.ld
+LDFLAGS = -Tkern/kernel.ld
 LDFLAGS += -m elf64lriscv
 
 CFLAGS = -Wall -Werror -O
@@ -33,7 +33,7 @@ all: kernel.elf
 
 main: main.o
 
-kernel.elf: entry.o start.o kern/libkern/string.o kern/libkern/proc.o kern/libkern/uart.o kern/libkern/panic.o kern/kalloc.o kern/libkern/memory.o kern/ispinlock.o kern/libkern/spinlock.o kern/libkern/string.o kern/libkern/mini-printf.o
+kernel.elf: kern/entry.o kern/start.o kern/libkern/string.o kern/libkern/proc.o kern/libkern/uart.o kern/libkern/panic.o kern/kalloc.o kern/libkern/memory.o kern/ispinlock.o kern/libkern/spinlock.o kern/libkern/string.o kern/libkern/mini-printf.o
 	@echo LD $@
 	@$(LD) $(LDFLAGS) -o $@ $^