board: beagle: beagleplay: Enable 32k crystal

Enable the external 32k crystal similar to that found on other
production AM62X board. The trim settings for the crystal is board
dependent, so the sequences tend to be board specific. Since this is
a configuration that needs to be done prior to DM managing the system
and all other muxes get set, do the same from R5 context.

Tested-by: Robert Nelson <robertcnelson@gmail.com>
Signed-off-by: Nishanth Menon <nm@ti.com>