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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Benjamin Tissoires <[e-mail]>

include/linux/string_choices.h

···
 {
 	return v ? "read" : "write";
 }
+#define str_write_read(v)		str_read_write(!(v))
 
 static inline const char *str_on_off(bool v)
 {