genirq: Remove unused irq_chip_generic:: {type,polarity}_cache

The type_cache and polarity_cache members of struct irq_chip_generic are
unused. Remove them both along with their kernel-doc.

Found by https://github.com/jirislaby/clang-struct

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Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240808104118.430670-2-jirislaby@kernel.org