lib/string_choices: add str_true_false()/str_false_true() helper

Add str_true_false()/str_false_true() helper to retur a "true" or "false"
string literal.  We found more than 10 cases currently exist in the tree. 
So these helpers can be used for these cases.


This patch (of 3):

Add str_true_false()/str_false_true() helper to return "true" or "false"
string literal.

Link: https://lkml.kernel.org/r/20240827024517.914100-1-lihongbo22@huawei.com
Link: https://lkml.kernel.org/r/20240827024517.914100-2-lihongbo22@huawei.com


Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Trond Myklebust <trondmy@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>