phy: exynos: fix building as a module

The top-level phy-samsung-usb2 driver may be configured as a
loadable module, which currently causes link errors because
of the dependency on the exynos{5250,4x12,4210}_usb2_phy_config
symbol. Solving this could be achieved by exporting these
symbols, but as the SoC-specific parts of the driver are not
currently built as modules, it seems better to just link
everything into one module and avoid the need for the export.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>