siflower: sf21 device tree fix
`i2c1` node was missing `resets`, so even when enabled, the driver would
not recognize it:
```
i2c_designware c101000.i2c: Unknown Synopsys component type: 0x00000000
```
With this fix, I2C pins on BPi-RV2 26-pin GPIO header are usable.
Signed-off-by: Rani Hod <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20969
Signed-off-by: Christian Marangi <[email protected]>