regulator: da9211: Fix wrong register name in error message

We tried to read the CONFIG_E register, not the CONTROL_E register.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: James Ban <james.ban.opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>