spmi: Return meaningful errors in spmi_controller_alloc()

spmi_controller_alloc() currently returns NULL to all types of errors,
which can be improved.

Use appropriate error code in returns and pass the errors from used
functions where possible.

Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://lore.kernel.org/r/20230824104101.4083400-6-fshao@chromium.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20231206231733.4031901-8-sboyd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

spmi: Introduce device-managed functions

Utilize the managed resource (devres) framework and add the following
devm_* helpers for the SPMI driver:

- devm_spmi_controller_alloc()
- devm_spmi_controller_add()

[sboyd@kernel.org: Rename to spmi-devres for module niceness, slap on
GPL module license]

Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://lore.kernel.org/r/20230824104101.4083400-2-fshao@chromium.org
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20231206231733.4031901-4-sboyd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>