net/sunrpc/cache: simplify code by using hex_pack_byte()

hex_pack_byte() is a fast way to convert a byte in its ASCII representation. We
may use it instead of custom approach.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

net/sunrpc/cache.c

@@ -1111,9 +1111,7 @@ void qword_addhex(char **bpp, int *lp, char *buf, int blen)
 		*bp++ = 'x';
 		len -= 2;
 		while (blen && len >= 2) {
-			unsigned char c = *buf++;
-			*bp++ = '0' + ((c&0xf0)>>4) + (c>=0xa0)*('a'-'9'-1);
-			*bp++ = '0' + (c&0x0f) + ((c&0x0f)>=0x0a)*('a'-'9'-1);
+			bp = hex_byte_pack(bp, *buf++);
 			len -= 2;
 			blen--;
 		}