ASoC: sti: regmap_field usage improvements

Merge series from Sander Vanheule <sander@svanheule.net>:

uni_player_parse_dt_audio_glue() allocates two regmap_field objects on
the device's regmap. However, error codes from these allocations are not
propagated correctly and the resources will leak on device removal.

These issues were found while looking for users of regmap_field_alloc(),
to assess the impact of adding a cleanup helper for regmap_field. It
appears this driver is the only (remaining) in-tree user of this
allocator. Since the resources are long-lived, it may as well switch to
devm_regmap_field_alloc().

As I don't have access to this hardware, these patches were only compile
tested on a UM build.