boards: x86: acrn : Add configurations for acrn_ehl_crb

Adding acrn configurations specific to the platform
on which acrn boots zephyr, Only the EHL specifc
configurations for now. Keeping the HW clock frequency to
1900Mhz for EHL and using the new APIc timer driver.

Signed-off-by: Aastha Grover <aastha.grover@intel.com>