staging/easycap: fix style issues in easycap_usb_probe function

fix some code styles and drop too verbose printouts
and non relevant code

Cc: Mike Thomas <rmthomas@sciolus.org>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>