OMAP2+: hwmod: Enable module in shutdown to access sysconfig

When calling the shutdown, the module may be already in idle.
Accessing the sysconfig register will then lead to a crash.
In that case, re-enable the module in order to allow the access
to the sysconfig register.

Signed-off-by: Miguel Vadillo <vadillo@ti.com>
Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>