gpio: tegra: fix unbalanced chained_irq_enter/exit

gpio: tegra: fix unbalanced chained_irq_enter/exit

commit 9e9509e38fbe034782339eb09c915f0b5765ff69 upstream.

When more than one GPIO IRQs are triggered simultaneously,
tegra_gpio_irq_handler() called chained_irq_exit() multiple
times for one chained_irq_enter().

Fixes: 3c92db9ac0ca3eee8e46e2424b6c074e2e394ad9
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
[Also changed the variable to a bool]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>