libcec: add patch to fix build on Blackfin

Blackfin uses a gcc 4.3 compiler, which does not support the
-Wno-psabi option. Since it is non essential, this commit adds a patch
to remove the usage of this option.

Fixes:

  http://autobuild.buildroot.net/results/3ab/3ab146583fa57ef7d6e67530b3274df1a844c7e1/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>