ghes_edac: Improve driver's printk messages

Provide a better infrastructure for printk's inside the driver:
	- use edac_dbg() for debug messages;
	- standardize the usage of pr_info();
	- provide warning about the risk of relying on this
	  driver.

While here, changes the size of a fake memory to 1 page. This is
as good or as bad as 1000 pages, but it is easier for userspace to
detect, as I don't expect that any machine implementing GHES would
provide just 1 page available ;)

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Conflicts:
	drivers/edac/ghes_edac.c