dm: usb: ehci: avoid possible NULL dereference

dm: usb: ehci: avoid possible NULL dereference

Currently we check in ehci_shutdown() if ctrl is NULL after
dereferencing it.

Before this we have already dereferenced ctrl, ctrl->hccr,
and ctrl->hcor in ehci_get_portsc_register(), ehci_submit_root(),
and hci_common_init().

A better approach is to already check ctrl, ctrl->hccr, and ctrl->hcor
during the initialization in ehci_register() and usb_lowlevel_init()
and signal an error here via the return code.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>