USB: gadget: functionfs: code cleanup

This patch removes some of the string registration from the
FunctionFS Gadget as composite layer can handle the
iManufacturer and iProduct for us.

It also removes some of the module parameters which were
redundant as well as changes the name of others to better much
the module parameter of the composite layer.

Other then that, it also fixes formatting of multiline comments
to match the coding style.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>