xilinx: Fix axi and mmc node names in mini configuration

xilinx: Fix axi and mmc node names in mini configuration

amba is not approved node name for simple-bus that's why use axi instead to
be aligned with other xilinx boards. Node reference is not changed that's
why there is no impact but also mini configuration will never gets to OS
that's why nothing should be affected from OS perspective (paths in /proc/
for example).

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/1b18a69ae47bdcb1a0795af7621d13bfecfc9861.1726219714.git.michal.simek@amd.com