Previously the min load_addr for HV image is hard coded to 0x10000000 when
CONFIG_RELOC is enabled, now use CONFIG_HV_RAM_START as its prefer minimum
address like setting of CONFIG_PHYSICAL_START do in Linux kernel.
With this patch, we can offload the CONFIG_HV_RAM_START algorithm to
acrn-config or manually set it in scenario XML on some special boards.
Tracked-On: #5275
Signed-off-by: Victor Sun <victor.sun@intel.com>