The timer driver is using some global variables to define some variables it has
to use in most of its functions, like the base address.

Use some container_of calls to have a single dynamic (and local) variable to
hold this content.

The only exception is in the !DT case, where the call chain to
at91sam926x_ioremap_pit and then at91sam926x_pit_init as init_time makes it
hard for the moment to pass the physical address of the timer.
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: NBoris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>