misc: fastrpc: remove unused definition

Remove unused INIT_MEMLEN_MAX define.

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Abhinav Asati <asatiabhi@codeaurora.org>
Signed-off-by: Vamsi Singamsetty <vamssi@codeaurora.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>