x86/kconfig: Remove outdated reference to Intel CPUs in CONFIG_SWIOTLB

Deleted the no longer valid example of which x86 CPUs lack a
hardware IOMMU, and moved the "If unsure..." statement to a new
line to follow the style of surrounding options.

Signed-off-by: Joe Millenbach <jmillenbach@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Cc: team-fjord@googlegroups.com
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Link: http://lkml.kernel.org/r/1346632700-29113-1-git-send-email-jmillenbach@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>