Now that coldfire is the only user of a custom asm/gpio.h, it seems
better to remove this as well, and have the same interface everywhere.
For the gpio_get_value()/gpio_set_value()/gpio_to_irq(), gpio_cansleep()
functions, the custom version is only a micro-optimization to inline the
function for constant GPIO numbers. However, in the coldfire defconfigs,
I was unable to find a single instance where this micro-optimization
was even used, and according to Geert the only user appears to be the
QSPI chip that is disabled everywhere.
The custom gpio_request_one() function is even less useful, as it is
guarded by an #ifdef that is never true.