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>
diff --git a/cmd/x86/Makefile b/cmd/x86/Makefile
index 7071614..144b1cf 100644
--- a/cmd/x86/Makefile
+++ b/cmd/x86/Makefile
@@ -2,4 +2,5 @@
 
 obj-y += mtrr.o
 obj-$(CONFIG_CMD_EXCEPTION) += exception.o
+obj-$(CONFIG_USE_HOB) += hob.o
 obj-$(CONFIG_HAVE_FSP) += fsp.o