Kconfig: Drop CONFIG_CMD_DS4510

This option enables a command in the driver. But the functions defined by
the driver are not called anywhere else in U-Boot. So it does not seem
useful to have this driver without its commands.

Drop this option, move the header file out of the common include/
directory and make all the function static.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Heiko Schocher <hs@denx.de>