regmap-i2c: Off by one in regmap_i2c_smbus_i2c_read/write()

The commit message says that we are allowed to read and write up to 32
bytes but the code only allows us to write 31 bytes.  In other words,
the ">=" should be changed to ">".  But this is already checked in
regmap_raw_read()/write() so we can just remove the if statemetents.

Fixes: 29332534 ("regmap-i2c: Add smbus i2c block support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Brown <broonie@kernel.org>