Input: ili210x - export ili251x version details via sysfs

Input: ili210x - export ili251x version details via sysfs

The ili251x firmware protocol permits readout of firmware version,
protocol version, mcu version and current mode (application, boot
loader, forced update). These information are useful when updating
the firmware on the il251x, e.g. to avoid updating the same firmware
into the device multiple times. The locking is now necessary to avoid
races between interrupt handler and the sysfs readouts.

Note that the protocol differs considerably between the ili2xxx devices,
this patch therefore implements this functionality only for ili251x that
I can test.

Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20210831202506.181927-2-marex@denx.de
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>