USB: ehci-s5p: Add phy driver support

Adding the phy driver to ehci-s5p. Keeping the platform data
for continuing the smooth operation for boards which still uses it

Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>