ASoC: xilinx: 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/20240507155540.24815-34-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/xilinx/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
-snd-soc-xlnx-i2s-objs      := xlnx_i2s.o
+snd-soc-xlnx-i2s-y      := xlnx_i2s.o
 obj-$(CONFIG_SND_SOC_XILINX_I2S) += snd-soc-xlnx-i2s.o
-snd-soc-xlnx-formatter-pcm-objs := xlnx_formatter_pcm.o
+snd-soc-xlnx-formatter-pcm-y := xlnx_formatter_pcm.o
 obj-$(CONFIG_SND_SOC_XILINX_AUDIO_FORMATTER) += snd-soc-xlnx-formatter-pcm.o
-snd-soc-xlnx-spdif-objs := xlnx_spdif.o
+snd-soc-xlnx-spdif-y := xlnx_spdif.o
 obj-$(CONFIG_SND_SOC_XILINX_SPDIF) += snd-soc-xlnx-spdif.o