regulator: fan53555: change fan53555_parse_dt() to read only DT parameters

Currently, fan53555_parse_dt() does a platform data allocation in
addition to reading device tree parameters. Move the memory
allocation out of fan53555_parse_dt() and change it only to parse
device tree parameters to match its name. This helps to expand
the function to read other device tree parameters.

CRs-Fixed: 968575
Change-Id: Id876d54bede15c73a298a6bfa68af7097115e36b
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>