drivers: pinmux: stm32f0: Add additional I2C pins.

Add additional pinmux definitions for I2C1 and I2C2 that are used
on the stm32f030 series SoCs. Additionally, correct the PF0 and PF1 I2C
functions, which were swapped.

Signed-off-by: Brian Kubisiak <brian@kubisiak.com>