mtd/ps3vram: Cleanup ps3vram driver messages

Cleanup the ps3vram driver messages.  Add a new struct device pointer
variable dev to struct ps3vram_priv and use dev_dbg(), pr_dbg(), etc.
where appropriate.
Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>