m68k/PCI: Fix a memory leak in an error handling path

If 'ioremap' fails, we must free 'bridge', as done in other error handling
path bellow.

Fixes: 19cc4c84 ("m68k/PCI: Replace pci_fixup_irqs() call with host bridge IRQ mapping hooks")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>