rtc: rx8581: drop needless struct rx8581

rtc: rx8581: drop needless struct rx8581

The memory pointed to by the ::rtc member is managed via devres, and
no code in this driver uses it past _probe().

We can drop it from the structure and just use a local temporary
variable, reducing runtime memory consumption by a few bytes.

Since this now means that the structure has just one member only left,
there  is no need anymore to allocate data for it and pass that around
via the various callbacks, just to extract that one member.

Instead, we can just pass that one member and avoid the extra memory
allocation for the containing struct, reducing runtime memory
consumption.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20250304-rtc-cleanups-v2-11-d4689a71668c@linaro.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>