Input: synaptics-rmi4 - handle incomplete input data

Commit 5b65c2a0 ("HID: rmi: check sanity of the incoming report") added
support for handling incomplete HID reports do to the input data being
corrupted in transit. This patch reimplements this functionality in the
function drivers so they can handle getting less valid data then they
expect.

Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>