Platform: corstone1000:flash_layout simplification

Complete the simplification of the flash layout.
The flash layout contains only the static definitions
that describe the static layout and the boundries of the dynamic
regions.

The dynamic regions addresses are known by the GPT parser.

Signed-off-by: Mohamed Omar Asaker <mohamed.omarasaker@arm.com>
Change-Id: I2bbbd2ff64962b906ec723ffcd082ac1cc92d769