uio: pruss: move simple allocations to dem_ equivalents

This change moves the simple allocations to their device-managed
equivalents.
This cleans up some error/exit paths.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201111112242.62116-1-alexandru.ardelean@analog.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>