docs: marvell: Update build manual

Update build manual
- remove irrelevant platforms and environemnt variables
- add links to BLE and mv_ddr Github repositories

Change-Id: Ie389c61f014751cdc0459b3f78c70ede694d27b8
Signed-off-by: Konstantin Porotchkin <kostap@marvell.com>
1 file changed