Revert "i2c: core: Dispose OF IRQ mapping at client removal time"

This reverts commit e4df3a0b
("i2c: core: Dispose OF IRQ mapping at client removal time")

Calling irq_dispose_mapping() will destroy the mapping and disassociate
the IRQ from the IRQ chip to which it belongs. Keeping it is OK, because
existent mappings are reused properly.

Also, this commit breaks drivers using devm* for IRQ management on
OF-based systems because devm* cleanup happens in device code, after
bus's remove() method returns.

Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Reported-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
[wsa: updated the commit message with findings fromt the other bug report]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Fixes: e4df3a0b