x86: apl: Add hex offsets for registers in FSP-S

When comparing hex dumps it is useful to see the offsets of the registers.
Add them in where they correspond to a multiple of 16.

Possibly it would be useful to have a a command to output the FSP values
in human-readable form, making use of the fsp_bindings implementation.

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