staging: tidspbridge: fix kernel oops in bridge_io_get_proc_load

The DSP shared memory area gets initialized only when
a COFF file is loaded.

If bridge_io_get_proc_load is called before loading a base
image into the DSP, the shared_mem member of the io manager
will be NULL, resulting in a kernel oops when it's dereferenced.

Also made some coding style changes to bridge_io_create.

Signed-off-by: Ionut Nicu <ionut.nicu@mindbit.ro>
Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>