platform/x86: dell-laptop: Allocate buffer before rfkill use

On machines using rfkill interface the buffer needs to have been
allocated before the initial use (memset) of it.

Reported-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>