There is no real phy driver, so s3c-hsudc just pokes the registers
itself. Improve this a little by making it a platform data callback
like we do for gpios.

There is only one board using this driver, and it's unlikely
that another would be added, so this is a minimal workaround.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200806182059.2431-9-krzk@kernel.org
[krzk: Include regs-s3c2443-clock.h in ifdef to fixup build on s3c6400]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>