MIPS: ralink: mt7621: use bitwise NOT instead of logical

It was the intention to reverse the bits, not make them all zero by
using logical NOT operator.

Fixes: cc19db8b31 ("MIPS: ralink: mt7621: do memory detection on KSEG1")
Suggested-by: Chuanhong Guo <gch981213@gmail.com>
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/ralink/mt7621.c

@@ -69,7 +69,7 @@ static bool __init mt7621_addr_wraparound_test(phys_addr_t size)
 	__raw_writel(MT7621_MEM_TEST_PATTERN, dm);
 	if (__raw_readl(dm) != __raw_readl(dm + size))
 		return false;
-	__raw_writel(!MT7621_MEM_TEST_PATTERN, dm);
+	__raw_writel(~MT7621_MEM_TEST_PATTERN, dm);
 	return __raw_readl(dm) == __raw_readl(dm + size);
 }