mplayer: not supported on sh2/sh2a

mplayer configure script says that sh2a is not supported.

Fixes:
http://autobuild.buildroot.org/results/0e530fd99c4b37782208ee0549be500220643999/



Signed-off-by: Gilles Talis <gilles.talis@gmail.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>