staging: tidspbridge: overwrite DSP error codes

When calling the DSP's remote functions, the DSP returns error
codes different from the ones managed by the kernel, the
function's return value is shared with the MPU using a shared
structure. This patch overwrites those error codes by kernel
specifics and deletes unnecessary code.

Signed-off-by: Rene Sapiens <rene.sapiens@ti.com>
Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>