Input: tsc2007 - add poll_delay parameter to platform data

Depending on the quality of the touch panel, the time for the X-, X+, Y-
and Y+ inputs to settle may vary. The poll_delay parameter can be used
to override the default of 1 millisecond.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Kwangwoo Lee <kwangwoo.lee@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>