i2c: octeon: check correct size of maximum RECV_LEN packet

I2C_SMBUS_BLOCK_MAX defines already the maximum number as defined in the
SMBus 2.0 specs. No reason to add one to it.

Fixes: 886f6f83

 ("i2c: octeon: Support I2C_M_RECV_LEN")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Robert Richter <rric@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>