linuxfb: Add config.test and configure support

The code is exactly the same as what is already done for DirectFB.

Change-Id: I3b84e67a3e999f692da4110f3ac9c82d98b0637c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>