sky2: Increase D3 delay again

Another platform requires even longer delay to make the device work
correctly after S3.

So increase the delay to 300ms.

BugLink: https://bugs.launchpad.net/bugs/1798921



Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>