EDAC, i82975x: Fix spelling mistake "reserverd" -> "reserved"

Fix a spelling mistake in a register layout description.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "Arvind R." <arvino55@gmail.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: https://lkml.kernel.org/r/20181120153304.1218-1-alexandre.belloni@bootlin.com