Include in next: Switch SpacemiT SoC tree's repo

Hi Linux-Next Maintainer,

  Previously, the SpacemiT SoC tree was hosted in github.com[1],
while now we've created a new kernel tree at kernel.org[2],
so please help to update the repo url for linux-next tree to the
new one, and the other info should being unchanged, that's:
  branch for master: for-next
  branch for pending-fixes: fixes
 
  I will also switch to new repo for sending next Pull-Request to
SoC tree maintainer.

  Thank you

[1] https://github.com/spacemit-com/linux
[2] https://git.kernel.org/pub/scm/linux/kernel/git/spacemit/linux.git/

-- 
Yixun Lan (dlan)