ASoC: Rename controls with a / in wm_hubs

This renames from a character / to : of controls. A / occurs below error
messages.

ASoC: Failed to create IN2RP/VXRP debugfs file
ASoC: Failed to create IN2LP/VXRN debugfs file

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>