Update "Getting Started with Qt for Android".

- Mention the dependencies that are necessary for 64-bit machines.
- Remove mention of JAVA_HOME, as that's done in Creator now.

Change-Id: I1bcb1f607fe80ba9089f746b3c01f40a66e6f6b7
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>