doc: release-notes-2.5: boards and SoCs: x86 ehl_crb acrn_ehl_crb

This adds a few lines for newly added board and SoC defintions
for Elkhart Lake (ehl_crb) and ACRN configurations (acrn_ehl_crb).

Signed-off-by: Jennifer Williams <jennifer.m.williams@intel.com>