libmad: remove

This is largely equivalent to the recipe in OE-Core apart from
LICENSE_FLAGS, insignificant patch differences, and an additional patch
for avr32 optimisation (and since there appears to be no public layer
for an avr32 machine, there's not a great deal of point in preserving
the latter).

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>