zynq-common: Define CONFIG_SYS_I2C_ZYNQ based on board config

Enable CONFIG_SYS_I2C_ZYNQ only if it has either I2C0 or I2C1
enabled in a board config.This fixes the issue of i2c error
during board init if board specific doesnt have either I2C0
or I2C1.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>