Move hp_accel to drivers/platform/x86

The hp_accel driver isn't a hardware monitoring driver, so it doesn't
belong to drivers/hwmon. Move it to drivers/platform/x86, assuming HP
doesn't ship non-x86 laptops.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Eric Piel <eric.piel@tremplin-utc.net>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Tested-by: Eric Piel <eric.piel@tremplin-utc.net>
Tested-by: Takashi Iwai <tiwai@suse.de>