Input preferences: Use BControlLook::ComposeIconSize().

And do some other cleanup while at it.

Fixes #17919.

input preferences: Updates code according to Haiku guidelines

These are the changes using tool clang-format with argument --style=haiku and the changes that were not according to guidelines have been removed.

Change-Id: I2d34370e1e0a112da895001bd220bb82b7086e90
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3827
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

Input: add icons to the DeviceList

Change-Id: I2eaebca0f0e91e3420b7e63a4a568f4e658af253
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2722
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>