tree-wide: convert open calls to remove spaces to skip_spaces() lib function

Makes use of skip_spaces() defined in lib/string.c for removing leading
spaces from strings all over the tree.

It decreases lib.a code size by 47 bytes and reuses the function tree-wide:
   text    data     bss     dec     hex filename
  64688     584     592   65864   10148 (TOTALS-BEFORE)
  64641     584     592   65817   10119 (TOTALS-AFTER)

Also, while at it, if we see (*str && isspace(*str)), we can be sure to
remove the first condition (*str) as the second one (isspace(*str)) also
evaluates to 0 whenever *str == 0, making it redundant. In other words,
"a char equals zero is never a space".

Julia Lawall tried the semantic patch (http://coccinelle.lip6.fr) below,
and found occurrences of this pattern on 3 more files:
    drivers/leds/led-class.c
    drivers/leds/ledtrig-timer.c
    drivers/video/output.c

@@
expression str;
@@

( // ignore skip_spaces cases
while (*str &&  isspace(*str)) { \(str++;\|++str;\) }
|
- *str &&
isspace(*str)
)

Signed-off-by: André Goddard Rosa <[email protected]>
Cc: Julia Lawall <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Richard Purdie <[email protected]>
Cc: Neil Brown <[email protected]>
Cc: Kyle McMartin <[email protected]>
Cc: Henrique de Moraes Holschuh <[email protected]>
Cc: David Howells <[email protected]>
Cc: <[email protected]>
Cc: Samuel Ortiz <[email protected]>
Cc: Patrick McHardy <[email protected]>
Cc: Takashi Iwai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/cachefiles/daemon.c

@@ -21,6 +21,7 @@
 #include <linux/mount.h>
 #include <linux/statfs.h>
 #include <linux/ctype.h>
+#include <linux/string.h>
 #include <linux/fs_struct.h>
 #include "internal.h"
 
@@ -257,8 +258,7 @@ static ssize_t cachefiles_daemon_write(struct file *file,
 		if (args == data)
 			goto error;
 		*args = '\0';
-		for (args++; isspace(*args); args++)
-			continue;
+		args = skip_spaces(++args);
 	}
 
 	/* run the appropriate command handler */