ARM: dts: aspeed-g6: Fix FSI master location

The FIS nodes were placed incorrectly in the device tree.

Fixes: 0fe4e304 ("ARM: dts: aspeed-g6: Describe FSI masters")
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>