i2c: qcom: geni: Add support for Standard, Fast and Fast plus modes

Add support for Standard, Fast and Fast plus modes of frequency.
Devicetree property should be added as per the slave requirement.
I2C driver sets to Fast mode if property is not specified
in DT file.

Signed-off-by: Shrey Vijay <shreyv@codeaurora.org>
Change-Id: Ie7c9d658f312c82d5a708ff624acbdcdcb3b8438