board: samsung: add Samsung Galaxy S9/S9+(SM-G96x0) board

Samsung S9 SM-G9600 - Snapdragon SDM845 version of the phone,
for China \ Hong Kong markets.
Has unlockable bootloader, unlike SM-G960U (American market version),
which allows running u-boot as a chain-loaded bootloader.

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Cc: Ramon Fried <rfried.dev@gmail.com>
Cc: Tom Rini <trini@konsulko.com>