mplayer: disable for FLAT

mplayer: disable for FLAT

mplayer uses a homegrown configure script that calls 'gcc -v | tail -1'
to find the gcc version. However, our toolchain wrapper adds
-Wl,-elf2flt to the gcc arguments. This triggers gcc to do an actual
compile (rather than just printing version info and exiting), and that
compile fails because of the missing definition of main(). The last
line of the output is therefore:
collect2: error: ld returned 1 exit status
and configure doesn't find a version in there. It then falls back to
using the host gcc instead, which breaks things completely a bit
further down the line.

Since mplayer probably isn't very useful on noMMU architectures anyway,
just disable it completely for FLAT.

Fixes:
http://autobuild.buildroot.net/results/58cf28a3acd518633a1d8ea719bc70aefbdfb311

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>