libmad: remove use of obsolete _thumb over-ride
The _thumb over-ride was first used by the libmad recipe in 2006 [1],
but should have been removed in 2007, when the libmad recipe dropped
support for building for thumb [2].
[1] http://git.openembedded.org/openembedded-core/commit/?id=
f1f8c5a6a7234a7b618f98efbb3d28e414890fa9
[2] http://git.openembedded.org/openembedded-core/commit/?id=
1aa801ac7b991790dce9cb2618d0816700e52a16
Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
