ACPI: remove "config ACPI_DEBUG_FUNC_TRACE"

Kconfig symbol ACPI_DEBUG_FUNC_TRACE was only used (through its
corresponding macro) in drivers/acpi/acpica/acmacros.h. That macro
was removed from that header in v3.8, with commit
86ff0e508f88eda6e479a897476026055831d2d8 ("ACPICA: Fix unmerged
acmacros.h divergences."), so ACPI_DEBUG_FUNC_TRACE can now be
removed too, as it is unused.

[rjw: Changelog]
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>