platform/x86: fujitsu-laptop: rename FUNC_RFKILL to FUNC_FLAGS

FUNC subfunction 0x1000 is currently referred to as FUNC_RFKILL, which
is misleading, because it handles more than just radio devices (also
lid, dock, LEDs).  Rename the FUNC_RFKILL constant to FUNC_FLAGS.
Replace "rfkill" with "flags" in the names of its associated fields
inside struct fujitsu_laptop.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
[kempniu: rebase patch, rewrite commit message]
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jonathan Woithe <jwoithe@just42.net>