mfd/omap1: htc-i2cpld: Convert to a pure GPIO driver

Instead of passing GPIO numbers pertaining to ourselves through
platform data, just request GPIO descriptors from our own GPIO
chips and use them, and cut down on the unnecessary complexity.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Cory Maccarrone <darkstar6262@gmail.com>
Cc: linux-omap@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220905115810.5987-1-linus.walleij@linaro.org