RK816 ldo write mask bit is always 1 after setting finished, but
when system start, the write mask bit is 0 even enable bit is 1.
So that rk816 regulator driver '.is_enabled()' returns disabled state
even the ldo is power on when system start, we need to initial write
mask bit as 1.
Change-Id: I8b5b83f33d668e4bdd1f96d77208931d25b8f6d9
Signed-off-by: Joseph Chen <chenjh@rock-chips.com>