HSI: ssi_protocol: Remove unused linux/gpio.h

linux/gpio.h is deprecated and subject to remove.
The driver doesn't use it, simply remove the unused header.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240508114150.958025-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>