i2c: mlxcpld: 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. I don't see a reason to add 1 here. Also, fix the errno
to what is suggested for this error.

Fixes: c9bfdc7c ("i2c: mlxcpld: Add support for smbus block read transaction")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Michael Shych <michaelsh@mellanox.com>
Tested-by: Michael Shych <michaelsh@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>