arm64: zynqmp: Setting default i2c clock frequency to 400kHz

Setting default i2c clock frequency for ZynqMP to maximum rate of 400kHz.
Current default value is 100kHz.

Signed-off-by: Varalaxmi Bingi <varalaxmi.bingi@amd.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/3034ec006c8b11e025904d4cc2524255523636f6.1686227766.git.michal.simek@amd.com