usb: r8a66597-hdc disable interrupts fix

This patch improves disable_controller() in the r8a66597-hdc
driver to disable all interrupts and clear status flags. It
also makes sure that disable_controller() is called during
probe(). This fixes the relatively rare case of unexpected
pending interrupts after kexec reboot.

Signed-off-by: Magnus Damm <damm@opensource.se>
Acked-by: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>