i2c: synquacer: Make synquacer_i2c_ops constant

Static structure synquacer_i2c_ops, of type i2c_adapter, is only used
when it is copied into a field of another structure. It is not itself
modified. Hence make it const to protect it from unintended
modification.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>