gpiolib: Optimize gpiochip_remove() when check for requested line

Here are the following optimizations have been done:
 - break the loop after first found requested line
  - due to above, drop redundant boolean variable
 - replace open coded variant of gpiochip_is_requested()
  - due to above, drop redundant pointer to struct gpio_desc
 - use 'unsigned int' instead of 'unsigned' for loop counter

Note, pointer to struct gpio_chip followed by pointer to struct gpio_device
is still valid, back link is not.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200225114725.839-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>