include/linux/cpumask.h: fix double string traverse in cpumask_parse

cpumask_parse() finds first occurrence of either or strchr() and
strlen().  We can do it better with a single call of strchrnul().

[akpm@linux-foundation.org: remove unneeded cast]
Link: http://lkml.kernel.org/r/20190409204208.12190-1-ynorov@marvell.com
Signed-off-by: Yury Norov <ynorov@marvell.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/cpumask.h

@@ -633,8 +633,7 @@ static inline int cpumask_parselist_user(const char __user *buf, int len,
  */
 static inline int cpumask_parse(const char *buf, struct cpumask *dstp)
 {
-	char *nl = strchr(buf, '\n');
-	unsigned int len = nl ? (unsigned int)(nl - buf) : strlen(buf);
+	unsigned int len = strchrnul(buf, '\n') - buf;
 
 	return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
 }