usb: musb: fix kernel panic during s2ram(v2)

This patch fixes kernel panic during s2ram, which is caused
by the below:

	- musb is not put into drv data of musb platform device if
	CONFIG_USB_MUSB_HDRC_HCD is defined

	- glue layer driver always get musb instance via platform_get_drvdata.

The patch fixes the issue by always puting musb into drv data
of musb platform device, which is doable even the platform device
is a host controller device.

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>