rawdev: add buffer stream IO

rawdev: add buffer stream IO

Introduce handlers for raw buffer enqueue and dequeue. A raw buffer
is essentially a void object which is transparently passed via the
library onto the driver.

Using a context field as argument, any arbitrary meta information
can be passed by application to the driver/implementation. This can
be any data on which driver needs to define the operation semantics.
For example, passing along a queue identifier can suggest the driver
the queue context to perform I/O on.

Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>