gpio: kempld: Add support for get/set multiple

gpio: kempld: Add support for get/set multiple

As the bus accesses are quiet slow with this device, supporting the
get/set multiple API can help with performences. The implementation
tries to keep the number of bus access to a minimum by checking
the mask to only read or write the needed bytes.

Signed-off-by: Alban Bedel <alban.bedel@lht.dlh.de>
Link: https://patch.msgid.link/20260311143120.2179347-4-alban.bedel@lht.dlh.de
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>