fstab: Add fake boot partition

Needed to complete the build without using custom releasetools

Change-Id: I96b07eeec933589095b057bc741cbd9a4a8c7296
Signed-off-by: Michael Bestas <mikeioannina@gmail.com>
Remove releasetools

No need to have all this duplicate code when we can override
non-writable boot partition with a single line fstab addition

Change-Id: Ie1a9301043ea4150318f5387d1a5eb6bc51775c4
Signed-off-by: Michael Bestas <mikeioannina@gmail.com>