HV: vlapic: minimize explicit casts by adjusting types

To minimize explicit casts, this patch adjusts the types of function parameters
and structure fields related to vlapic and update the types in the internal
implementation accordingly.

Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Acked-by: Dong Eddie <eddie.dong@intel.com>

Author: junjiemao1