platform/firenze: Fix branch-to-null crash

When the bus alloc and free methods were removed we missed a case in the
Firenze platform slot code that relied on the the bus-specific method to
the bus pointer in the request structure. This results in a
branch-to-null during boot and a crash. This patch fixes it by
initialising it manually here.

Fixes: 801462f ("core/i2c: Remove bus specific alloc and free callbacks")
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

platforms/ibm-fsp/firenze-pci.c

@@ -835,6 +835,7 @@ static void firenze_pci_setup_power_mgt(struct pci_slot *slot,
 	plat_slot->req->rw_len		= 1;
 	plat_slot->req->completion	= firenze_i2c_req_done;
 	plat_slot->req->user_data	= slot;
+	plat_slot->req->bus		= plat_slot->i2c_bus;
 
 	firenze_pci_slot_fixup(slot, info);