arm64: dts: ti: k3-*: fix fss node dtbs check warnings

arm64: dts: ti: k3-*: fix fss node dtbs check warnings

Fix these fss node warnings that dtbs_check throws:

fss@47000000: $nodename:0: 'fss@47000000' does not match
'^([a-z][a-z0-9\\-]+-bus|bus|localbus|soc|axi|ahb|apb)(@.+)?$'

By renaming fss to bus.

Cc: Nishant Menon <nm@ti.com>
Suggested-by: Andrew Davis <afd@ti.com>
Signed-off-by: Dhruva Gole <d-gole@ti.com>
Reviewed-by: Reid Tonking <reidt@ti.com>
Link: https://lore.kernel.org/r/20230810081847.277094-1-d-gole@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>