ASoC: sti: 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/20240507155540.24815-28-tiwai@suse.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sti/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 # STI platform support
-snd-soc-sti-objs := sti_uniperif.o uniperif_player.o uniperif_reader.o
+snd-soc-sti-y := sti_uniperif.o uniperif_player.o uniperif_reader.o
 
 obj-$(CONFIG_SND_SOC_STI) += snd-soc-sti.o