usb: ehci-exynos: Change to use phy provided by the generic phy framework

Add the phy provider, supplied by new Exynos-usb2phy using
Generic phy framework.
Keeping the support for older USB phy intact right now, in order
to prevent any functionality break in absence of relevant
device tree side change for ehci-exynos.
Once we move to new phy in the device nodes for ehci, we can
remove the support for older phys.

Signed-off-by: Kamil Debski <k.debski@samsung.com>
[gautam.vivek@samsung.com: Addressed review comments from mailing list]
[gautam.vivek@samsung.com: Kept the code for old usb-phy, and just
added support for new exynos5-usb2phy in generic phy framework]
[gautam.vivek@samsung.com: Edited the commit message]
Signed-off-by: Vivek Gautam <gautam.vivek@samsung.com>
Cc: Jingoo Han <jg1.han@samsung.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>