USB: EHCI: Add bus glue for GRLIB GRUSBHC controller

This patch adds support for the GRLIB GRUSBHC EHCI controller from
Aeroflex Gaisler. The controller is typically found on LEON/GRLIB
SoCs.

Tested on GR-LEON4-ITX with with little endian interface and on
LEON3 system on GR-PCI-XC5V development board for big endian
controller.

Signed-off-by: Jan Andersson <jan@gaisler.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>