lib/string_choices: Add str_plural() helper

Add str_plural() helper to replace existing open implementations
used by many drivers and help improve future user facing messages.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20240214165015.1656-1-michal.wajdeczko@intel.com
Signed-off-by: Kees Cook <keescook@chromium.org>

lib/string_choices: Add str_write_read() helper

Add an inversed variant of str_read_write(), i.e. str_write_read().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230703185222.50554-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

lib/string_choices: Add str_high_low() helper

Add str_high_low() helper to return 'high' or 'low' string literal.
Also add an inversed variant, i.e. str_low_high().

All the same for str_hi_low().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

lib/string_helpers: Split out string_choices.h

Some users may only need the string choice APIs. Split
the respective header, i.e. string_choices.h. Include
it in the string_helpers.h for backward compatibility.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>