Revert "sunxi: f1c100s: Drop SYSRESET to enable reset functionality"

The original Allwinner F1C100 .dtsi imported from the Linux kernel tree
used the wrong compatible string for the watchdog timer, so the Allwinner
DM reset driver was not working properly. We worked around this by
disabling the SYSRESET driver, so the hardcoded SPL reset driver took
over.
Now the issue was fixed in the DTs in mainline Linux, and we synced the
fixed .dtsi file into U-Boot, so drop the hack and use the normal U-Boot
proper reset infrastructure.

This reverts commit cfcf1952.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>