gpiolib: coldfire: remove custom asm/gpio.h

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.

Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>