x86: Add a simple command to show FSP HOB information

FSP builds a series of data structures called the Hand-Off-Blocks
(HOBs) as it progresses through initializing the silicon. These data
structures conform to the HOB format as described in the Platform
Initialization (PI) specification Volume 3 Shared Architectual
Elements specification, which is part of the UEFI specification.

Create a simple command to parse the HOB list to display the HOB
address, type and length in bytes.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>