package/rocksdb: bump to version 6.10.1

- Update indentation of hash file (two spaces)
- Remove first patch (already in version)
- Add link to upstream PR in second patch
- Add upstream patch to fix build on powerpc (patch does not apply
  cleanly on current version)
- Update hash of README.md, slack forum added with
  https://github.com/facebook/rocksdb/commit/cf342464caf8155ab60f7a48e39a8d6ae3138a7a

Fixes:
 - http://autobuild.buildroot.org/results/242db7139ce5dd6ece4a1eb50a1aa47c841a41b7



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>