hw/isa/i82378: Remove intermediate IRQ forwarder

hw/isa/i82378: Remove intermediate IRQ forwarder

When the i82378 model was added in commit a04ff940974 ("prep:
Add i82378 PCI-to-ISA bridge emulation") the i8259 model was
not yet QOM'ified. This happened later in commit 747c70af78f
("i8259: Convert to qdev").

Directly dispatch ISA IRQs to 'cpu_intr' output IRQ
by removing the intermediate i82378_request_out0_irq()
handler. Rename ISA IRQs array as 'isa_irqs_in' to
emphasize these are input IRQs.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230210163744.32182-4-philmd@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>