Tools\FitGen: Add extra parameter fixed FIT address

Add "-T <FixedFitLocation>" parameter to provide fixed
FIT address on flash region. When this parameter is set
to a valid address in the input FD/FV file, tool will
directly generate FIT on this address.

It's users' responsibilities to reserve enough size for
FIT table and option modules on the target location,
otherwise, FIT Gen process will fail.

Cc: Chen Christine <yuwei.chen@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>

Signed-off-by: fanwang2intel <fan.wang@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>