net: dsa: mv88e6xxx: fix handling of upper half of STATS_TYPE_PORT

Currently, the upper half of a 4-byte STATS_TYPE_PORT statistic ends
up in bits 47:32 of the return value, instead of bits 31:16 as they
should.

Fixes: 6e46e2d8 ("net: dsa: mv88e6xxx: Fix u64 statistics")
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -785,7 +785,7 @@ static uint64_t _mv88e6xxx_get_ethtool_stat(struct mv88e6xxx_chip *chip,
 			err = mv88e6xxx_port_read(chip, port, s->reg + 1, &reg);
 			if (err)
 				return U64_MAX;
-			high = reg;
+			low |= ((u32)reg) << 16;
 		}
 		break;
 	case STATS_TYPE_BANK1: