iichid(4): Always use wMaxInputLength bytes as input report length

Lower values may result in non-acknowledged interrupts. E.g. ITE5570 device
found in ASUS TUF. Greater values may result in read failures. E.g. GXTP7863
device found on MateBookPro 2023.

Investigated by: huanghwh@gmail.com
PR: 289353
MFC after: 1 week
fixes: 36027361f9cf ("iichid: Stop using split I²C bus transactions")

(cherry picked from commit 8f496952e3e6cdd531675a44b84b3f1954532afb)