Input: synaptics-rmi4 - f12: read only the object data on attention

When F12 data is not supplied by the transport as attention data, the
attention handler reads the whole F12 data packet on every interrupt,
although only Data1 (the object reports) is consumed. The remaining
data registers are never used.

On SMBus this transfer is the dominant per-frame cost. On a ThinkPad
P14s Gen 2i with a Synaptics TM3471-030 (i801 SMBus) the F12 data
packet is 79 bytes, of which Data1 is the first 32. Reading 79 bytes
takes about 17.4 ms and reading 32 bytes about 7.3 ms. With the full
read the touchpad reports at about 43 Hz (median 23.0 ms between
frames), and fast swipes yield only a handful of frames, so they are
mostly lost to pointer acceleration and smoothing.
Reading only Data1 raises the report rate to about 65 Hz (median
15.3 ms between frames), measured with a finger on the same machine.

Compute the size of the leading registers up to and including Data1 at
probe time and read only that much. The attention data path (hid-rmi)
is unchanged.

Signed-off-by: Dmitry Mikushin <dmitry@kernelgen.org>
Link: https://patch.msgid.link/20261026142648.2567233-3-dmitry@kernelgen.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>