rtc: bq32000: add delay between RTC reads

rtc: bq32000: add delay between RTC reads

When the RTC is used on systems without a interrupt line, userspace
tools like `hwclock` fall back to a frequent polling loop to synchronize
with the edge of the next second.

On the BQ32000, this aggressive polling can temporarly lock the register
refresh cycle, because the continuous transfers prevent the hardware from
updating the buffer. This results in stale data reads or select() timeouts
in userspace.

This patch introduces a delay before reading the RTC registers in order to
provide a sufficient idle time for the hardware to sync with the register
buffer.

Signed-off-by: Adriana Stancu <adriana@arista.com>
Link: https://patch.msgid.link/20260416142151.3385827-1-adriana@arista.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>