fecdec: Avoid fecdec output buffer overruns.

fecdec: Avoid fecdec output buffer overruns.

The size of the buffer tree pool of the amp filter is 64K, which
is smaller than BTRN_MAX_PENDING of buffer_tree.c (96K). The latter
value is used in btr_node_status() as follows. If input for a buffer
tree node is available and there is less than BTRN_MAX_PENDING bytes
in the output queue of the node, the function returns 1 to indicate
that the node should continue to process its input.

This can result in a fatal error condition when the buffer tree pool
fills up completely. Avoid this by increasing the pool size to 128K.