mmc: renesas_sdhi: fix error code in renesas_sdhi_probe()

If devm_regulator_register() fails then propagate the error code.  Don't
return success.

Fixes: fae80a99 ("mmc: renesas_sdhi: Add support for RZ/G3E SoC")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/dc39e555-8ef7-4a39-9253-65bcf3e50c01@stanley.mountain


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>