input: Questionable return in input server

[kallisti5]

clang actually found this one...

C++ objects/haiku/x86_64/release/servers/input/MouseSettings.o 
../src/servers/input/MouseSettings.cpp:430:9: error: cannot initialize return object of type 'MouseSettings *' with an rvalue of type 'int'
        return B_OK;
               ^~~~
../headers/os/support/Errors.h:53:19: note: expanded from macro 'B_OK'
#define B_OK                                            ((int)0)
                                                        ^~~~~~~~
1 error generated.

​https://git.haiku-os.org/haiku/tree/src/servers/input/MouseSettings.cpp#n403

I'm actually not sure why gcc thinks that's valid

[kallisti5]

Fix submitted here: ​https://review.haiku-os.org/c/haiku/+/3303

[waddlesplash]

Fix merged in hrev54630.