ACPICA: fix -Wfallthrough

ACPICA commit 4b9135f5774caa796ddf826448811e8e7f08ef2f

GCC 7.1 gained -Wimplicit-fallthrough to warn on implicit fallthrough,
as well as __attribute__((__fallthrough__)) and comments to explicitly
denote that cases of fallthrough were intentional. Clang also supports
this warning and statement attribute, but not the comment form.

Robert Moore provides additional context about the lint comments being
removed. They were for "an old version of PC-Lint, which we don't use
anymore." Drop those.

This will help us enable -Wimplicit-fallthrough throughout the Linux
kernel.

Suggested-by: Robert Moore <robert.moore@intel.com>
Reported-by: Jon Hunter <jonathanh@nvidia.com>

Link: https://github.com/acpica/acpica/commit/4b9135f5


Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>