gpio: mxc: fix both_edges bit operations

gpio_set_irq_type() can be called concurrently for different pins on
the same port.  The IRQ core serializes per irq descriptor, but
different pins have different descriptors, so on SMP systems two
concurrent gpio_set_irq_type() calls for pins on the same port run
without mutual exclusion.

The read-modify-write of port->both_edges is performed outside the
port-wide scoped_guard(gpio_generic_lock_irqsave) section, so
concurrent updates for different pins can overwrite each other,
causing missed interrupts or stuck IRQ lines on dual-edge triggered
pins.

The original uniprocessor MXC SoCs were not affected; the race
became reachable on multi-core i.MX7 and i.MX8 SoCs that reuse this
driver.

Convert both_edges from u32 to unsigned long and use set_bit(),
clear_bit(), and test_bit() to make the modifications atomic.

Fixes: 910862ec092c ("mxc: emulate GPIO interrupt on both-edges")
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20261013-gpio-mxc-cleanup-v7-2-c4d769587d3e@nxp.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>