i2c: mlxcpld: Allow flexible polling time setting for I2C transactions

Allow polling time setting according to I2C frequency supported across
the system. For base frequency 400 KHz and 1 MHz set polling time is set
four times less than for system with base frequency 100KHz.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>