vc_mem: tidy up debug procfs code

Remove commented-out procfs code, which was generating
a warning and no longer worked. Replace this with
equivalent debugfs entries.

Signed-off-by: Luke Diamand <luked@broadcom.com>
vc_mem: tidy up debug printing

Replace explicit use of printk() with pr_XXX() calls to
better conform to kernel coding style.

Signed-off-by: Luke Diamand <luked@broadcom.com>