pinctrl: samsung: Separate per-bank init and runtime data

Currently the driver mixes constant init data with runtime data, which
is far from being elegant and can invite potential hard to track issues.
This patch intends to solve this by introducing a new
samsung_pin_bank_data structure to hold only constant data known at
compile time, which can be copied to main samsung_pin_bank struct used
at runtime.

In addition, thanks to this change, all per-bank initdata can be marked
with const and __initconst keywords and dropped after init completes.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>