remoteproc: mtk_scp: Use dev_err_probe() where possible

remoteproc: mtk_scp: Use dev_err_probe() where possible

Simplify the probe function, where possible, by using dev_err_probe().
While at it, as to increase human readability, also remove some
unnecessary forced void pointer casts that were previously used in
error checking.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220124120915.41292-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>