Input: bcm5974 - adjust major/minor to scale

By visual inspection, the reported touch_major and touch_minor axes
are a factor of two too small. Presumably the device actually reports
the semi-major and semi-minor axes. Corrected with this patch.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>