ARM: module: Add ".ref.text" to arm unwind tables

Functions inside kernel modules that use __ref
will end up being placed in .ARM.exidx.ref.text
section by gcc.

Currently while adding sections to arm unwind tables
we don't add consider adding these funtions.

Hence, if we turn slub debug on by default we end up
with the messages of this sort :

	unwind: Index not found bf0011e0

This is because slub debug saves stack trace of
allocation's and free's. Therefore we end up seeing
a flood of these messages in dmesg.

Fix this by adding .ref.text section to arm unwind tables.

Change-Id: I78783d3620f7f4f9c85ec260063f959cd96967f0
Signed-off-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>