ASoC: kirkwood: Use *-y instead of *-objs in Makefile

*-objs suffix is reserved rather for (user-space) host programs while
usually *-y suffix is used for kernel drivers (although *-objs works
for that purpose for now).

Let's correct the old usages of *-objs in Makefiles.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20240507155540.24815-15-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/kirkwood/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
-snd-soc-kirkwood-objs := kirkwood-dma.o kirkwood-i2s.o
+snd-soc-kirkwood-y := kirkwood-dma.o kirkwood-i2s.o
 
 obj-$(CONFIG_SND_KIRKWOOD_SOC) += snd-soc-kirkwood.o
 
-snd-soc-armada-370-db-objs := armada-370-db.o
+snd-soc-armada-370-db-y := armada-370-db.o
 
 obj-$(CONFIG_SND_KIRKWOOD_SOC_ARMADA370_DB) += snd-soc-armada-370-db.o