yocto: Remove references to fvp-rd-kronos MACHINE

Arm Auto Solutions is a generic layer that will be used for
fvp-rd-kronos alongside future automotive platforms. So:
 * Replace :fvp-rd-kronos overrides with :baremetal and/or
   :virtualization accordingly.
 * Rename the fvp_rd_kronos_image_features bbclass to
   arm_auto_solutions_image_features.
 * Rename machine-specific .inc files.
 * Remove COMPATIBLE_MACHINE definitions where possible.
 * Remove other references to fvp-rd-kronos specifically.

Signed-off-by: Peter Hoyes <peter.hoyes@arm.com>