x86: fix CONFIG_NONPROMISC_DEVMEM prompt and help text

Here is an attempt to translate the prompt and help text into something
which is legible and, as a bonus, correct.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>