KabylakeOpenBoardPkg/AspireVn7Dash572G/DxeBoardInitLib: Fix byte shift

Since the time is sent to the EC byte-by-byte, perform shift by a byte
multiple of bits. Also update some comments.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Signed-off-by: Benjamin Doron <benjamin.doron00@gmail.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>