Input: pxrc - flatten probe code

Instead of splitting probe code into separate USB and input setup, flatten it.
This allows for easier inspection of order of set up steps, since the probe code
is reasonably small.

Move input-related initialization (phys) from USB block to input block.

Reviewed-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Tested-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>