x86: Add a common HOB library

FSP (CONFIG_HAVE_FSP) and Slim Bootloader (CONFIG_SYS_SLIMBOOTLOADER)
consume HOB (CONFIG_USE_HOB) data from the each HOB list pointer.
Add a common HOB library in lib/hob.c and include/asm/hob.h.

Signed-off-by: Aiden Park <aiden.park@intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>