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

ASoC: stm: 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/20240507155540.24815-29-tiwai@suse.de
Signed-off-by: Mark Brown <broonie@kernel.org>