Input: himax_hx83112b - implement MCU register reading

Implement reading from the MCU in a more universal fashion. This allows
properly handling reads of more than 4 bytes using the AHB FIFO
implemented in the chip.

Signed-off-by: Felix Kaechele <felix@kaechele.ca>
Link: https://lore.kernel.org/r/20240620145019.156187-4-felix@kaechele.ca


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>