readme: Update list of supported platforms
readme: Update list of supported platforms

Change-Id: I13b7b16a13f51bcb83098d7c55701f9ee03859a8
Signed-off-by: Antonio Nino Diaz <5c24ff39be768bf31f4deee44042a11772cfd02a@arm.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware