USB: host: ehci-sead3: Remove SEAD-3 EHCI code

USB: host: ehci-sead3: Remove SEAD-3 EHCI code

The SEAD-3 board is now probing its EHCI controller using the generic
EHCI driver & its generic-ehci device tree binding. Remove the unused
SEAD-3 specific EHCI code.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14052/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>