ramips: add support for Tenda 3G150B

Add suport for Tenda 3G150B:
- cpu: Ralink RT5350F
- flash: 4MB
- ram: 32MB
- 1x USB 2.0
- 1x RJ45
- one reset button
- battery powered (BP-4L, 3.7V 1450mAh)

Signed-off-by: Cezary Jackiewicz <cezary.jackiewicz@gmail.com>

SVN-Revision: 44073