regulator: fan53555: add support for Halo HL7509 buck converter

Halo HL7509 is a digitally programmable buck converter that
outputs a voltage from 600 to 1230 mV from an input voltage of
2.5 to 5.5 V. Since the register mappings are compatible with
FAN53555, add a new vendor ID to support it.

CRs-Fixed: 968575
Change-Id: I0083a7ada311d624731e43755cfd371b2364fb39
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>