test_hexdump: use memcpy instead of strncpy

BugLink: https://bugs.launchpad.net/bugs/1818813

commit b1286ed7 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

lib/test-hexdump.c

@@ -81,7 +81,7 @@ static void __init test_hexdump(size_t len, int rowsize, int groupsize,
 		const char *q = *result++;
 		size_t amount = strlen(q);
 
-		strncpy(p, q, amount);
+		memcpy(p, q, amount);
 		p += amount + 1;
 	}
 	if (i)