net/macb: fix the peripheral version test

We currently need two checks of the peripheral version in MACB_MID register.
One of them got out of sync after modification by 8a013a9c (net: macb:
Include multi queue support for xilinx ZynqMP ethernet version).
Fix this in macb_configure_caps() so that xilinx ZynqMP will be considered
as a GEM flavor.

Fixes: 8a013a9c ("net: macb: Include multi queue support for xilinx ZynqMP
ethernet version")

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Punnaiah Choudary Kalluri <punnaia@xilinx.com>
Cc: <stable@vger.kernel.org> #4.0 (if it doesn't make it for -final)
Signed-off-by: David S. Miller <davem@davemloft.net>