usb: musb: get rid of MUSB_LOGLEVEL and use parameter

We can change debugging level on the fly via
/sys/module/musb_hdrc/parameters/debug.

We can also get rid of the LOGLEVEL facility in Kconfig
and rely only in module parameter.

Cc: Anand Gadiyar <gadiyar@ti.com>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>