arm: boot: dts: am4372: enable dwc3 suspend PHY quirk

Whenever Suspend PHY bit is set on AM437x devices,
USB will not work due to Set EP Configuration command
always failing.

This was only found after a recent commit 2164a47 (usb:
dwc3: set SUSPHY bit for all cores, which will be merged
for v3.19) added a missing *required* step to dwc3
initialization. Synopsys Databook requires that we enable
Suspend PHY bit after initialization but that, unfortunately,
breaks AM437x.

Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>