ACPI: replace kmalloc+memcpy with kmemdup

Replace the combination of kmalloc() and memcpy() in acpi_run_osc()
with a single call to kmemdup().

[rjw: Changelog]
Signed-off-by: Andrei Epure <epure.andrei@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>