ARM: dts: am57xx-beagle-x15: remove extcon_usb1

USB1 controller is hardwired to be used as Host only port so
we don't need to check ID pin state and can get rid of extcon_usb1.

This also reduces USB1 controller's and so eSATA power's dependency
with EXTCON. This fixes eSATA port with multi_v7_defconfig.

Cc: Franklin S Cooper Jr. <fcooper@ti.com>
Cc: Vagrant Cascadian <vagrant@debian.org>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Tested-by: Franklin S Cooper Jr. <fcooper@ti.com>
[tony@atomide.com: updated to describe what it fixes]
Signed-off-by: Tony Lindgren <tony@atomide.com>