stagine/easycap: make functions regset and regget static

regget and regset functions are used only from within
easycap_low.c so they can be static
Move the functions to avoid forward declarations
Move GET and SET macro definitions into the c-file

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