nds32: Fill all TLB entries with kernel image mapping

We use earlycon replace with early_printk and doesn't use
early_io_map() to create UART mapping. It is not necessary
to reserve the one way in TLB for now.

It didn't make sense if use direct-mapped and reserve one
way at the same time. It allow the direct-mapped now.
Signed-off-by: NZong Li <zong@andestech.com>
Signed-off-by: NGreentime Hu <greentime@andestech.com>

arch/nds32/kernel/head.S

@@ -123,14 +123,7 @@ _image_size_check:
         andi    $r0, $r0, MMU_CFG_mskTBS
         srli    $r6, $r6, MMU_CFG_offTBW
         srli    $r0, $r0, MMU_CFG_offTBS
-        /*
-         * we just map the kernel to the maximum way - 1 of tlb
-         * reserver one way for UART VA mapping
-         * it will cause page fault if UART mapping cover the kernel mapping
-         *
-         * direct mapping is not supported now.
-         */
-        beqz    $r6, __error                 ! MMU_CFG.TBW = 0 is direct mappin
+	addi    $r6, $r6, #0x1               ! MMU_CFG.TBW value -> meaning
         addi    $r0, $r0, #0x2               ! MMU_CFG.TBS value -> meaning
         sll     $r0, $r6, $r0                ! entries = k-way * n-set
         mul     $r6, $r0, $r5                ! max size = entries * page size