armv8: layerscape: Fix the sequence of changing MMU table

This patch follows the break-before-make process when making changes
to MMU table. MMU is disabled before changing TTBR to avoid any
potential race condition.

Signed-off-by: York Sun <york.sun@nxp.com>

arch/arm/cpu/armv8/fsl-layerscape/cpu.c

@@ -181,21 +181,14 @@ static inline void final_mmu_setup(void)
 	setup_pgtables();
 	gd->arch.tlb_addr = tlb_addr_save;
 
-	/* flush new MMU table */
-	flush_dcache_range(gd->arch.tlb_addr,
-			   gd->arch.tlb_addr + gd->arch.tlb_size);
+	/* Disable cache and MMU */
+	dcache_disable();	/* TLBs are invalidated */
+	invalidate_icache_all();
 
 	/* point TTBR to the new table */
 	set_ttbr_tcr_mair(el, gd->arch.tlb_addr, get_tcr(el, NULL, NULL),
 			  MEMORY_ATTRIBUTES);
-	/*
-	 * EL3 MMU is already enabled, just need to invalidate TLB to load the
-	 * new table. The new table is compatible with the current table, if
-	 * MMU somehow walks through the new table before invalidation TLB,
-	 * it still works. So we don't need to turn off MMU here.
-	 * When EL2 MMU table is created by calling this function, MMU needs
-	 * to be enabled.
-	 */
+
 	set_sctlr(get_sctlr() | CR_M);
 }