misc: atsha204a: Remove duplicate CRC-16 implementation

ATSHA204A uses bit-reversed checksum of standard CRC-16 with polynomial
x^16 + x^15 + x^2 + 1.

This ATSHA204A specific checksum can be calculated just by using common
U-Boot functions bitrev16() and crc16().

So replace custom driver CRC-16 implementation by common U-Boot functions.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>