fix(tc): tc2 bl1 start address shifted by one page

Change [1] is specific to TC2 model and breaks former TC0/TC1 test
configs.
BL1 start address is 0x0 on TC0/TC1 and 0x1000 from TC2 onwards.
Fix by adding conditional defines depending on TARGET_PLATFORM build
flag.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/15917



Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I51f77e6a61ca8eaa6871c19cabe9deb1288f5a9d