kstrtox: use "unsigned int" more

gcc does generates stupid code sign extending data back and forth. Help by using "unsigned int".

add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-61 (-61)
function old new delta
_parse_integer 128 123 -5

It _still_ does generate useless MOVSX but I don't know how to delete it:

0000000000000070 <_parse_integer>:

			...
  a0:   89 c2                   mov    edx,eax
  a2:   83 e8 30                sub    eax,0x30
  a5:   83 f8 09                cmp    eax,0x9
  a8:   76 11                   jbe    bb <_parse_integer+0x4b>
  aa:   83 ca 20                or     edx,0x20
  ad:   0f be c2      ===>      movsx  eax,dl         <===
			useless
  b0:   8d 50 9f                lea    edx,[rax-0x61]
  b3:   83 fa 05                cmp    edx,0x5

Patch also helps on embedded archs which generally only like "int". On arm "and 0xff" is generated which is waste because all values used in comparisons are positive.

---

 lib/kstrtox.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

@@ -52,12 +52,14 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
 	res = 0;
 	rv = 0;
 	while (1) {
+		unsigned int c = *s;
+		unsigned int lc = c | 0x20; /* don't tolower() this line */
 		unsigned int val;
 
-		if ('0' <= *s && *s <= '9')
-			val = *s - '0';
-		else if ('a' <= _tolower(*s) && _tolower(*s) <= 'f')
-			val = _tolower(*s) - 'a' + 10;
+		if ('0' <= c && c <= '9')
+			val = c - '0';
+		else if ('a' <= lc && lc <= 'f')
+			val = lc - 'a' + 10;
 		else
 			break;