mfd: omap-usb-tll: Configure ULPIAUTOIDLE

The idle mode needs to be only disabled for UTMIAUTOIDLE while
ULPIAUTOIDLE can be enabled.

This matches the TLL_CHANNEL_CONF_i register configuration for ehci-tll
in the Motorola Linux kernel tree for Wrigley 3G LTE modem on droid 4
and the modem still stays responsive.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>