vsprintf: Use non-atomic bitmap API when applicable

The 'set' bitmap is local to this function. No concurrent access to it is
possible.
So prefer the non-atomic '__[set|clear]_bit()' function to save a few
cycles.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/1abf81a5e509d372393bd22041eed4ebc07ef9f7.1638023178.git.christophe.jaillet@wanadoo.fr

lib/vsprintf.c

@@ -3564,7 +3564,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 				++fmt;
 
 			for ( ; *fmt && *fmt != ']'; ++fmt, ++len)
-				set_bit((u8)*fmt, set);
+				__set_bit((u8)*fmt, set);
 
 			/* no ']' or no character set found */
 			if (!*fmt || !len)
@@ -3574,7 +3574,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			if (negate) {
 				bitmap_complement(set, set, 256);
 				/* exclude null '\0' byte */
-				clear_bit(0, set);
+				__clear_bit(0, set);
 			}
 
 			/* match must be non-empty */