drivers: isdn: use new hex_to_bin() method

Remove own implementation of hex_to_bin().

Signed-off-by: Andy Shevchenko <ext-andriy.shevchenko@nokia.com>
Acked-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/isdn/gigaset/capi.c

@@ -169,17 +169,6 @@ static inline void ignore_cstruct_param(struct cardstate *cs, _cstruct param,
 			 msgname, paramname);
 }
 
-/*
- * convert hex to binary
- */
-static inline u8 hex2bin(char c)
-{
-	int result = c & 0x0f;
-	if (c & 0x40)
-		result += 9;
-	return result;
-}
-
 /*
  * convert an IE from Gigaset hex string to ETSI binary representation
  * including length byte
@@ -191,7 +180,7 @@ static int encode_ie(char *in, u8 *out, int maxlen)
 	while (*in) {
 		if (!isxdigit(in[0]) || !isxdigit(in[1]) || l >= maxlen)
 			return -1;
-		out[++l] = (hex2bin(in[0]) << 4) + hex2bin(in[1]);
+		out[++l] = (hex_to_bin(in[0]) << 4) + hex_to_bin(in[1]);
 		in += 2;
 	}
 	out[0] = l;