Versatile Express: Fix NOR flash 0 address and remove flash alias

Versatile Express: Fix NOR flash 0 address and remove flash alias

In the A series memory map (implemented in the Cortex A15 CoreTile), the
first NOR flash bank (flash 0) is mapped to address 0x08000000, while
address 0x00000000 can be configured as alias to either the first or the
second flash bank. This patch fixes the definition of flash 0 address,
and for simplicity removes the alias definition.

Signed-off-by: Francesco Lavra <francescolavra.fl@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>