ACPI: sbshc: Fix fall-through warning for Clang

ACPI: sbshc: Fix fall-through warning for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a
fallthrough warning by simply dropping the empty default case at
the bottom.

This contributes to the ongoing efforts to globally enable
-Wimplicit-fallthrough for Clang.

Link: https://github.com/KSPP/linux/issues/115
Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/lkml/CAJZ5v0hLYWKX__oZdcCY0D20pNqpw8SkiTPOCNOtpqe--QLp4Q@mail.gmail.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>