hw/isa: Inline and remove one-line isa_init_irq()

isa_init_irq() has become a trivial one-line wrapper for isa_get_irq().
It can therefore be removed.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> (tpm_tis_isa)
Acked-by: Corey Minyard <cminyard@mvista.com> (isa_ipmi_bt, isa_ipmi_kcs)
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20220301220037.76555-8-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20220307134353.1950-14-philippe.mathieu.daude@gmail.com>
Reviewed-by: Bernhard Beschow <shentey@gmail.com>