ARM: 7816/1: CONFIG_KUSER_HELPERS: fix help text

commit ac124504ecf6b20a2457d873d0728a8b991a5b0c upstream.

Commit f6f91b0d9fd9 ("ARM: allow kuser helpers to be removed from the
vector page") introduced some help text for the CONFIG_KUSER_HELPERS
option which is rather contradictory.

Let's fix that, and improve it a little.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>