firmware: Relocate when load address is not equal to link address

This patch extends fw_base to relocate to link address whenever
firmware load address is not equal to link address.

The relocation will not work when load start to load end overlap
link start to link end.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Tested-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>