isdn: remove ishexdigit() in regard to isxdigit()

Samll cleanup in drivers/isdn/gigaset/capi.c where own implementation of
isxdigit() has been changed to kernel native one.

Signed-off-by: Andy Shevchenko <ext-andriy.shevchenko@nokia.com>
Acked-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/isdn/gigaset/capi.c b/drivers/isdn/gigaset/capi.c
index 20ebcee..6643d65 100644
--- a/drivers/isdn/gigaset/capi.c
+++ b/drivers/isdn/gigaset/capi.c
@@ -171,20 +171,6 @@
 }
 
 /*
- * check for legal hex digit
- */
-static inline int ishexdigit(char c)
-{
-	if (c >= '0' && c <= '9')
-		return 1;
-	if (c >= 'A' && c <= 'F')
-		return 1;
-	if (c >= 'a' && c <= 'f')
-		return 1;
-	return 0;
-}
-
-/*
  * convert hex to binary
  */
 static inline u8 hex2bin(char c)
@@ -204,7 +190,7 @@
 {
 	int l = 0;
 	while (*in) {
-		if (!ishexdigit(in[0]) || !ishexdigit(in[1]) || l >= maxlen)
+		if (!isxdigit(in[0]) || !isxdigit(in[1]) || l >= maxlen)
 			return -1;
 		out[++l] = (hex2bin(in[0]) << 4) + hex2bin(in[1]);
 		in += 2;