usb: musb: tusb6010: fix error path in tusb_probe()

On platform_device_add() failure, the TUSB6010 glue layer forgets to call
platform_device_put() -- probably due to a typo...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>