introduce gprintk()

introduce gprintk()

... and convert several gdprintk()-s to it, as the next patch will make
them no-ops in non-debug builds.

Note that as a non-debug facility this does not print file name and
line number of the origin, to people are expected to use meaningful and
easily distinguishable messages (i.e. just like with plain printk()).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>