gpio: fix a possible access to null pointer in 'libsoc_gpio_callback_interrupt_cancel()'
gpio: fix a possible access to null pointer in 'libsoc_gpio_callback_interrupt_cancel()'

If 'libsoc_gpio_callback_interrupt()' was not called, or it did not success,
a call to 'libsoc_gpio_callback_interrupt_cancel()' accesses to 'gpio->callback'
that is a null pointer.

Signed-off-by: Tatiana Leon <8c4753e861fecbb16ba9ebac0b105a2d4612071d@digi.com>

hlummis/libsoc,yegorich/libsoc,hlummis/libsoc,jackmitch/libsoc,hlummis/libsoc,jackmitch/libsoc,yegorich/libsoc,hlummis/libsoc,jackmitch/libsoc,yegorich/libsoc