Tools\FitGen: Add extra parameter to input the Top Flash Address

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2981



Add extra parameter to the Fit Gen Tool to input the Top Flash Address.
Default Address should be 4GB and if some one inputs new address,
tool must consume that address instead of Default address (4GB).

Signed-off-by: cbduggap <chinni.b.duggapu@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>

Signed-off-by: cbduggap <chinni.b.duggapu@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>