xtensa: nommu: don't provide arch_get_unmapped_area

Nommu unconditionally provides arch_get_unmapped_area that always
returns -ENOMEM.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/syscall.c

@@ -57,6 +57,7 @@ asmlinkage long xtensa_fadvise64_64(int fd, int advice,
 	return sys_fadvise64_64(fd, offset, len, advice);
 }
 
+#ifdef CONFIG_MMU
 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
 		unsigned long len, unsigned long pgoff, unsigned long flags)
 {
@@ -93,3 +94,4 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
 			addr = COLOUR_ALIGN(addr, pgoff);
 	}
 }
+#endif