ARM: OMAP4+: AESS: enable internal auto-gating during initial setup

Enable the AESS auto-gating control bit during AESS hwmod setup.  This
fixes the following boot warning on OMAP4:

omap_hwmod: aess: _wait_target_disable failed

Without this patch, the AESS IP block does not indicate to the PRCM
that it is idle after it is reset.  This prevents some types of SoC
power management until something sets the auto-gating control bit.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>
Cc: Benoît Cousson <b-cousson@ti.com>
Cc: Péter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Tony Lindgren <tony@atomide.com>