sony-laptop: fix SNC buffer calls when SN06 returns Integers

SN06 in some cases returns an Integer instead of a buffer. While the
code handling the return value was trying to cope with the difference,
the memcpy call was not making any difference between the two types of
acpi_object union. This regression was introduced in 3.5.
While there also rework the return value logic to improve readability.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=48671


Cc: <stable@vger.kernel.org>
Cc: Fabrizio Narni <shibotto@gmail.com>
Cc: <mus.svz@gmail.com>
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>