Nokia RX-51: Move comment about CONFIG_SYS_TEXT_BASE to correct place

In commit commit 278b90ce786f ("configs: Migrate CONFIG_SYS_TEXT_BASE") was
moved definition for CONFIG_SYS_TEXT_BASE option but author probably forgot
to move also comment for lines which are moving. So do it now!

Signed-off-by: Pali Rohár <pali@kernel.org>
diff --git a/board/nokia/rx51/lowlevel_init.S b/board/nokia/rx51/lowlevel_init.S
index 7b1e50d..1466d97 100644
--- a/board/nokia/rx51/lowlevel_init.S
+++ b/board/nokia/rx51/lowlevel_init.S
@@ -155,7 +155,14 @@
 	mov	pc, r2
 
 
-/* Copy u-boot to address CONFIG_SYS_TEXT_BASE */
+/*
+ * Copy u-boot to address CONFIG_SYS_TEXT_BASE
+ *
+ * Nokia X-Loader loading secondary image to address 0x80400000
+ * NOLO loading boot image to random place, so it doesn't really
+ * matter what is set in CONFIG_SYS_TEXT_BASE. We have to copy
+ * u-boot to CONFIG_SYS_TEXT_BASE address.
+ */
 
 copy_uboot_start:
 	/* r0 - start of u-boot before */