misc: atsha204a: Add support for atsha204 chip

atsha204 chip is predecessor of atsha204a chip. Current U-Boot driver
atsha204a-i2c.c can use both atsha204 and atsha204a chips because it does
not call specific functions to just one of these chips.

So just add compatible string for atsha204.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Heiko Schocher <hs@denx.de>