[ALSA] sound: ice1712: unused structs

Don't need to declare a struct when defining a structure layout.  Both
of these structs are unused.
sound/pci/ice1712/revo.c:39:3: warning: symbol 'revo51' was not declared. Should it be static?
sound/pci/ice1712/phase.c:54:3: warning: symbol 'phase28' was not declared. Should it be static?

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>