test_hexdump: use memcpy instead of strncpy

New versions of gcc reasonably warn about the odd pattern of

	strncpy(p, q, strlen(q));

which really doesn't make sense: the strncpy() ends up being just a slow
and odd way to write memcpy() in this case.

Apparently there was a patch for this floating around earlier, but it
got lost.
Acked-again-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_hexdump.c

@@ -99,7 +99,7 @@ static void __init test_hexdump_prepare_test(size_t len, int rowsize,
 		const char *q = *result++;
 		size_t amount = strlen(q);
 
-		strncpy(p, q, amount);
+		memcpy(p, q, amount);
 		p += amount;
 
 		*p++ = ' ';