mfd: sec: Remove unused platform data members

The Samsung PMIC drivers for early chipsets like S5M8767 stored quite a
lot in platform data (struct sec_platform_data).  The s5m8767 regulator
driver currently references only some of its fields.  Newer regulator
drivers (e.g. s2mps11) use even less platform data fields.

Clean up the structure to reduce memory footprint and source code size.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>