xtensa: fix noMMU build on cores with MMU

Commit bf15f86b34 ("xtensa: initialize MMU before jumping to reset
vector") calls MMU management functions even when CONFIG_MMU is not
selected. That breaks noMMU build on cores with MMU.

Don't manage MMU when CONFIG_MMU is not selected.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/setup.c

@@ -540,7 +540,7 @@ subsys_initcall(topology_init);
 
 void cpu_reset(void)
 {
-#if XCHAL_HAVE_PTP_MMU
+#if XCHAL_HAVE_PTP_MMU && IS_ENABLED(CONFIG_MMU)
 	local_irq_disable();
 	/*
 	 * We have full MMU: all autoload ways, ways 7, 8 and 9 of DTLB must