staging/easycap: make oss ops function static in sound_oss.c

1. make oss ops function static
2. move around code so to avid forward declarations
3. move OSS ioclts from ioctl.c to sound_oss.c

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