k210: dts: align fpioa node with Linux

Linux kernel fpioa pinctrl driver expects the sysctl phandle and the
power bit offset of the fpioa device to be specified as a single
property "canaan,k210-sysctl-power".
Replace the "canaan,k210-sysctl" and "canaan,k210-power-offset"
properties with "canaan,k210-sysctl-power" to satisfy the Linux kernel
requirements. This new property is parsed using the existing function
dev_read_phandle_with_args().

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>