regulator: bcm590xx: fix vbus name

The vbus regulator was not getting its name set. This results
in the sysfs entry being empty. The lack of a bcm590xx_regs[]
table entry also upsets Coverity runs. Add the table entry
so the name gets set properly.

Signed-off-by: Graham Williams <graham.williams@linaro.org>
Acked-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>