remoteproc/pruss: purge userspace types

No functional changes, but usage of userspace types
within the kernel is frowned upon; so replace them
with kernel appropriate types.

Fixes: c6f6211e ("remoteproc/pruss: add a remoteproc driver for PRUSS in TI SoCs")
Signed-off-by: Felipe Balbi <balbi@ti.com>
[afd@ti.com: rebase changes onto current baseline]
Signed-off-by: Andrew F. Davis <afd@ti.com>
[s-anna@ti.com: minor commit description edits]
Signed-off-by: Suman Anna <s-anna@ti.com>