USB: EHCI: make ehci-s5p a separate driver

Separate the  Samsung S5P/EXYNOS host controller driver from ehci-hcd
host code so that it can be built as a separate driver module.
This work is part of enabling multi-platform kernels on ARM;
however, note that other changes are still needed before S5P/EXYNOS can
be booted with a multi-platform kernel. We currently expect those
to get merged for 3.10.

With the infrastructure added by Alan Stern in patch 3e023203


"USB: EHCI: prepare to make ehci-hcd a library module", we can
avoid this problem by turning a bus glue into a separate
module, as we do here for the s5p bus glue.

In V4 (arnd)
 - revert some of the pointless changes.
 - fix allocation of s5p specific data structure.

In V3:
 - Detailed commit message added here, why this patch is required.
 - MODULE_LICENSE is GPL v2.
 - Added .extra_priv_size to eliminate the separate allocation of
   the s5p_ehci_hcd structure and removed .reset function pointer
   initialization.
 - Arranged  #include's in alphabetical order.
 - After using extra_priv_size initialization, struct usb_hcd *hcd
   is redundant and can be removed from the probe function.
 - Eliminated s5p_ehci_phy_enable,contents of statements moved
   into the s5p_ehci_probe
 - Eliminated s5p_ehci_phy_disable, contents of statements moved into
   the s5p_ehci_remove.

In V2:
 - Tegra patch related changes removed from this patch.

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>