ASoC: cs35l56-shared-test: Fix possible null pointer dereference

ASoC: cs35l56-shared-test: Fix possible null pointer dereference

The struct regmap_config is dereferenced before its check. Also, after
it is checked priv->reg_offset is assigned to regmap_config->reg_base,
making the removed line redundant.

Detected by Smatch:
sound/soc/codecs/cs35l56-shared-test.c:681 cs35l56_shared_test_case_base_init()
warn: variable dereferenced before check 'regmap_config' (see line 665)

Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
Link: https://patch.msgid.link/20260523211522.522616-1-ethantidmore06@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>