MAINTAINERS: Reclaim the P: tag for Maintainer Entry Profile

Fixup some P: entries to be M: and delete the others that do not include an
email address. The P: tag will be used to indicate the location of a
Profile for a given MAINTAINERS entry.

Cc: Joe Perches <joe@perches.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/157462918794.1729495.10838545318307341653.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>