Input: ili210x - implement pressure reporting for ILI251x

Input: ili210x - implement pressure reporting for ILI251x

The ILI251x seems to report pressure information in the 5th byte of
each per-finger touch data element. On the available hardware, this
information has the values ranging from 0x0 to 0xa, which is also
matching the downstream example code. Report pressure information
on the ILI251x.

Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20201224071238.160098-1-marex@denx.de
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>