display: ssd1306: add some init delay

Seems like the SSD1306 controller needs a bit of time after power up
before it can take i2c commands. This causes problems with
microcontrollers that have no other delays in the startup sequence, like
rpi_pico.

There's currently no good way of modeling this in Zephyr right now, and
there's also no clear indication of how much time the device needs in
the datasheet that I could find, but it seems like 10ms is enough for
that to start reliably so add a delay in the ssd1306 init function to
ensure that at least that time has passed from system power up.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>