Allow refresh serdes configs during runtime

[xzhangxa]

• Add 2 attrs to refresh max9295/max9296 configs anytime by user.
• When switching formats of IR stream, do not refresh all the serdes
  settings, so other streaming streams won't be interrupted. Only the
  necessary addresses are set now.

Test steps for using the new attributes:

1. Boot the board and use D457 as usual;
2. Power off the max9296 board then power on, to lose all settings of max9295/9296;
3. Run commands below.

echo 1 | sudo tee /sys/bus/i2c/drivers/max9295/30-0040/refresh_setting
echo 1 | sudo tee /sys/bus/i2c/drivers/max9296/30-0048/refresh_setting

4. Start streams of D457 as usual, still works. IR stream format will still be the last used one, matching the v4l2 node format.

And when switching formats of IR stream, the serdes settings being changed are reduced to only the necessary ones. So now if another stream is streaming, it won't be interrupted (on current master, the streaming could be seen stopped for 1 or 2 seconds then go on again), with the new changes the other stream won't be affected.

[dmipx]

That's great! Thank you!

[dmipx]

isn't it better to have max9295/6 as modules and not compile it to kernel?
current config is
CONFIG_I2C_IOEXPANDER_SER_MAX9295=y
CONFIG_I2C_IOEXPANDER_DESER_MAX9296=y

[xzhangxa]

isn't it better to have max9295/6 as modules and not compile it to kernel? current config is CONFIG_I2C_IOEXPANDER_SER_MAX9295=y CONFIG_I2C_IOEXPANDER_DESER_MAX9296=y

We didn't modify the default kernel config of Jetson, so it's just the original setting.

[xzhangxa]

This PR is ready to review/merge. Besides the refresh attributes, another fix and cleanup is added. Please see the updated first comment for details.

[jnzw]

Looks good to me.

[dmipx]

this part looks complicated, can you elaborate why we discard 4 registers?

[xzhangxa]

You can see originally we only have map_pipe_y8_opt and map_pipe_y12i_opt, they are used for y8_y8i and y12i separately, the first 4 addr/val pairs are same, only the last one is different.

Now it's split to a common map_pipe_opt with the 4 common addr/val, and map_pipe_y8_opt and map_pipe_y12i_opt for the last different pair. When switching only the last pair is refreshed. The patch file instead of the diff in code makes it less obvious :)