usb: fhci-hcd: Allocate pram dynamically.

MPC832x does not have enough MURAM to do fixed MURAM allocation.
Change to dynamic allocation.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>