Documentation: firmware-guide: gpio-properties: Spelling and style fixes

Documentation: firmware-guide: gpio-properties: Spelling and style fixes

 - Use consistent style for active-high and active-low
 - For C and ASL code snippets use 4-space indentation consistently
 - Interleave case examples with the explanations of the certain case
 - Remove or add commas when appropriate

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://patch.msgid.link/20250626130109.215848-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>