Based on Tony Lindgren's work for omap34xx, this patch applies the same
functionality to the AM3517.

The following can be tested via sysfs with the following to ensure the SGX
module gets enabled and disabled properly:

0x00010201

Bus error

Cc: Filip Matijević <filip.matijevic.pz@gmail.com>
Cc: "H. Nikolaus Schaller" <hns@goldelico.com>
Cc: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Cc: moaz korena <moaz@korena.xyz>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Cc: Philipp Rossak <embed3d@gmail.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Adam Ford <aford173@gmail.com>
[tony@atomide.com: updated subject, dropped rstctrl info]
Signed-off-by: Tony Lindgren <tony@atomide.com>