USB: ehci-fsl: Add power management support

EHCI FSL controller preserve its state during sleep mode, so nothing
fancy needs to be done.

Though, during 'deep sleep' mode (as found in MPC831x CPUs) the
controller turns off and needs to be reinitialized upon resume.

This patch adds support for hibernation and resuming after deep sleep.
Based on Dave Liu and Jerry Huang's work[1].

[1] http://www.bitshrine.org/gpp/linux-fsl-2.6.24.3-MPC8315ERDB-usb-power-mangement.patch

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>