i2c: sun8i_rsb: Only do non-DM pin setup for non-DM I2C

When the DM_I2C driver is loaded, the pin setup is done automatically
from the device tree by the pinctrl driver.

Clean up the code in the process: remove #ifdefs and recognize that the
pin configuration is the same for all sun8i/sun50i SoCs, not just those
which select CONFIG_MACH_SUN8I.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>